Multi-layer paper peelable into at least two thin sheets

ABSTRACT

Disclosed is a multi-layer paper suitable as a material for preparing heat-sensitive stencil printing masters. The multi-layer paper is produced by combining a plurality of thin paper layers by paper making. The multi-layer paper has a peel strength of 10 N/m or less and may be delaminated into at least two tissue sheets.

TECHNICAL FIELD

This invention relates to a multi-layer paper peelable into at least twotissue sheets, to a method of producing a tissue sheet using themulti-layer paper, to a tissue sheet obtained from the multi-layerpaper, to a reinforced tissue sheet material having a tissue sheet towhich a reinforcing member is bonded, to a reinforced multi-layer papermaterial having a reinforcing sheet bonded to a multi-layer paper, to amethod of producing such a reinforced tissue sheet material using thereinforced multi-layer paper material, to a material for producing aheat-sensitive stencil printing master, to a heat-sensitive stencilprinting master, to a heat-sensitive stencil paper and to a method ofproducing a heat-sensitive stencil printing master.

As a method of preparing a tissue paper for use as a porous substratefor a heat-sensitive stencil printing master, there is known a method inwhich fibers having a small diameter are subjected to wet paper making.In such a tissue paper preparing method, there is a limitation inthickness of the producible tissue paper. Thus, it is difficult toprepare tissue paper having a small basis weight. Additionally, there isa problem because production costs are high.

JP-B-H06-57920 discloses a method of preparing a thin paper formed of asynthetic fiber. According to the disclosed method, a wet paper (A) ofcellulose fibers is combined with a wet paper (B) polyester fibers bypaper making and the combined paper is dried to obtain a 2-layer paper.The 2-layer paper is heat-bonded under pressure at a temperature higherthan the softening point of the polyester fibers. The cellulose fiberlayer is then peeled off to leave a thin paper of the polyester fibers.

The known method is, however, not satisfactory from the standpoint ofproduction apparatus, thermal energy and production costs, because ofthe necessity of a specific heat press bonding device for a stepperformed at a temperature higher than the softening point of thesynthetic fiber for heat-bonding the synthetic fiber layer of amulti-layer paper obtained after a drying step. Further, the multi-layerpaper obtained after the heat press bonding step of the conventionalmethod has a problem because it is difficult to harmonize both theinterlayer peelability and the strengths of tissue paper obtainedtherefrom. When a tissue sheet having high strengths is produced, it isnecessary to increase the temperature at which the heat-bonding isperformed. This results in very poor interlayer peelability. On theother hand, when a multi-layer paper having good interlayer peelabilityis desired, it is necessary to use a low heat-bonding temperature. Inthis case, the strengths of the tissue paper obtained from themulti-layer paper are very low. Additionally, since the thin paper ofthe synthetic fibers prepared by delamination of the multi-layer paperhas been subjected to a press bonding treatment at a high temperature,the density thereof is high. With the known method, it is very difficultto produce a thin paper having a density of 0.4 g/cm³ or less.

DISCLOSURE OF THE INVENTION

The objective problems of the present invention are as follows.

-   (1) To provide a multi-layer paper having small peel strength and    excellent peelability in a multi-layer paper peelable into two or    more tissue sheets.-   (2) To provide a method which can produce a multi-layer paper having    excellent peelability at an economically advantageous manner without    using a specific heat press-bonding step.-   (3) To provide a high grade tissue sheet having a low basis weight    and a low density using the multi-layer paper having excellent    peelability and a method of producing same.-   (4) To provide a reinforced tissue sheet material having a tissue    sheet to which a reinforcing member is bonded.-   (5) To provide a reinforced multi-layer paper material having a    reinforced member bonded to the multi-layer paper.-   (6) To provide a method of producing a reinforced tissue sheet    material using the above reinforced multi-layer paper material.-   (7) To provide a material for preparing a heat-sensitive stencil    printing master, which has can give a high grade material having a    low basis weight and a low density.-   (8) To provide a high grade heat-sensitive stencil printing master    having a low density and a low basis weight and a method of    preparing such a stencil printing master.

The present inventors have made intensive studies with a view to solvingthe above objective problems and have completed the present invention.

Thus, in accordance with the present invention, there are provided thefollowing inventions:

-   (1) A multi-layer paper comprising at least two paper layers    combined by a paper making method, characterized in that said    multi-layer paper has at least one peelable paper layer interface    having a peel strength of 10 N/m or less, and in that said    multi-layer paper is peelable into at least two tissue sheets at    said peelable paper layer interface.-   (2) A multi-layer paper as recited in (1) above, wherein one of the    two adjacent paper layers between which said peelable paper layer    interface is defined is mainly made of cellulose fibers, while the    other paper layer is mainly made of synthetic fibers including    binder fibers, said binder fibers exhibiting binder effect at a    temperature of 90-120° C.-   (3) A multi-layer paper as recited in (2) above, wherein said    synthetic fibers are heteroatom-containing synthetic fibers.-   (4) A multi-layer paper as recited in (2) above, wherein said    synthetic fibers are polyolefin fibers.-   (5) A multi-layer paper as recited in any one of (2)-(4) above,    wherein said binder fibers are composite fibers and are contained in    an amount of 20-100 mass %.-   (6) A multi-layer paper as recited in any one of (2)-(4) above,    wherein said binder fibers are single-component fibers and are    contained in an amount of 20-70 mass %.-   (7) A multi-layer paper as recited in (5) above, wherein said binder    fibers are composite fibers having a core-sheath structure, said    sheath being comprised of a resin exhibiting a binder effect at a    temperature of 90-120° C.-   (8) A multi-layer paper as recited in (7) above, wherein the resin    constituting said sheath is a polyester resin.-   (9) A multi-layer paper as recited in (7) above, wherein the resin    constituting said sheath is a polyolefin resin or an ethylene-vinyl    acetate copolymer resin.-   (10) A multi-layer paper as recited in (1) above, wherein one of the    two adjacent paper layers between which said peelable paper layer    interface is defined is made of synthetic fibers including composite    binder fibers having a low melting point component made of a    polyolefin resin or an ethylene-vinyl acetate copolymer resin, while    the other paper layer is made of synthetic fibers including    composite binder fibers having a low melting point component made of    a polyester resin, both-of said binder fibers exhibiting binder    effect at a temperature of 90-120° C.-   (11) A multi-layer paper as recited in (10) above, wherein said one    paper layer made of synthetic fibers including composite binder    fibers having a low melting point component made of a polyolefin    resin or an ethylene-vinyl acetate copolymer resin is mainly made of    polyolefin fibers, and wherein said binder fibers of said one paper    layer exhibits binder effect at a temperature of 90-120° C. and is    contained in an amount of 20-100 mass %.-   (12) A multi-layer paper as recited in (10) above, wherein said the    other paper layer made of synthetic fibers including composite    binder fibers having a low melting point component made of a    polyester resin is mainly made of heteroatom-containing synthetic    fibers, and wherein said binder fibers exhibit binder effect at a    temperature of 90-120° C. and is contained in an amount of 20-100    mass %.-   (13) A multi-layer paper as recited in any one of (2)-(8) above,    wherein said one layer mainly made of cellulose fibers contains a    release agent.-   (14) A multi-layer paper as recited in any one of (2)-(8) above,    wherein said the other layer mainly made of synthetic fibers are    made of polyester fibers.-   (15) A multi-layer paper as recited in any one of (1)-(14) above,    wherein one of the two adjacent paper layers between which said    peelable interface is defined is made of relatively more highly    oriented fibers as compared with that of the other paper layer.-   (16) A multi-layer paper as recited in any one of (1)-(15) above,    wherein at least one of the two surfaces of two adjacent paper    layers which surfaces define said peelable interface has been    subjected to a smoothing treatment.-   (17) A multi-layer paper as recited in any one of (1)-(16) above,    wherein at least one of said tissue sheet peeled from said    multi-layer paper has a basis weight of 1-20 g/m².-   (18) A multi-layer paper as recited in any one of (2)-(8) above,    wherein the tissue sheet peeled from said multi-layer paper and made    of the synthetic fibers has a density of not greater than 0.35    g/cm³.-   (19) A multi-layer paper as recited in (3) above, wherein the tissue    sheet peeled from said multi-layer paper and made of the    heteroatom-containing synthetic fibers has a density of not greater    than 0.35 g/cm³.-   (20) A multi-layer paper comprising at least three paper layers    unified by a paper making method, characterized in that said    multi-layer paper has, as an intermediate layer, at least one paper    layer which can cause intralayer delamination and which has a peel    strength of 10 N/m or less, and in that said multi-layer paper is    peelable into at least two tissue sheets at said intermediate paper    layer.-   (21) A multi-layer paper as recited in (20) above, wherein each of    the paper layers adjacent to said intermediate layer is mainly made    of synthetic fibers including at least binder fibers, said binder    fibers exhibiting binder effect at a temperature of 90-120° C.-   (22) A multi-layer paper as recited in (21) above, wherein said    binder fibers are composite fibers and are contained in an amount of    20-100 mass %.-   (23) A multi-layer paper as recited in (21) above, wherein said    binder fibers are single-component fibers and are contained in an    amount of 20-70 mass %.-   (24) A multi-layer paper as recited in (22) above, wherein said    binder fibers are composite fibers having a core-sheath structure,    said sheath being comprised of a resin exhibiting a binder effect at    a temperature of 90-120° C.-   (25) A multi-layer paper as recited in any one of (20)-(24) above,    wherein said paper layer which can cause intralayer delamination is    mainly made of polyester fibers.-   (26) A multi-layer paper as recited in (25) above, wherein said    paper layer made of said polyester fibers has a basis weight of 2-8    g/m².-   (27) A multi-layer paper as recited in any one of (20)-(24) above,    wherein said paper layer which can cause intralayer delamination is    mainly made of cellulose fibers.-   (28) A multi-layer paper as recited in (25) above, wherein said    paper layer made of said cellulose fibers has a basis weight of 5-10    g/m².-   (29) A method of forming tissue sheets, comprising providing a    multi-layer paper as recited in any one of (1)-(19) above, and    delaminating said multi-layer paper at said peelable paper layer    interface to obtain at least two tissue sheets.-   (30) A method as recited in (29) above, wherein at least one of said    tissue sheets has a basis weight of 2-20 g/m².-   (31) A method of forming tissue sheets, comprising providing a    multi-layer paper as recited in any one of (20)-(28) above, and    delaminating said multi-layer paper at said paper layer which can    cause intralayer delamination to obtain at least two tissue sheets.-   (32) A method as recited in (31) above, wherein at least one of said    tissue sheets has a basis weight of 2-20 g/m².-   (33) A tissue sheet obtained by a method as recited in any one of    (29)-(32) above and having a basis weight of 2-20 g/m².-   (34) A reinforced tissue sheet material, comprising a tissue sheet    as recited in (33) above and a reinforcing member bonded thereto.-   (35) A reinforced tissue sheet material as recited in (34) above,    wherein said reinforcing member is a polymer film or a metal foil.-   (36) A reinforced multi-layer paper material, comprising a    multi-layer paper as recited in any one of (1)-(28) above and a    reinforcing member bonded to at least one of the both sides of said    multi-layer paper.-   (37) A reinforced multi-layer paper material as recited in (36)    above, wherein said reinforcing member is a polymer film or a metal    foil.-   (38) A method of preparing a reinforced tissue sheet material,    comprising providing a reinforced multi-layer paper material as    recited in (36) or (37) above, and delaminating said multi-layer    paper to obtain a reinforced tissue sheet material having said    reinforcing member bonded thereto.-   (39) A porous support material for producing a heat-sensitive    stencil printing master, comprising a multi-layer paper as recited    in any one of (1)-(28) above.-   (40) A material for producing a heat-sensitive stencil printing    master, comprising a laminate obtained by bonding a thermoplastic    polymer film to at least one side of a multi-layer paper as recited    in any one of (1)-(28) above.-   (41) A heat-sensitive stencil printing master comprising a porous    support, and a thermoplastic polymer film bonded to said porous    support, wherein said porous support is a tissue paper as recited    in (33) above.-   (42) A method of preparing a heat-sensitive stencil printing master,    comprising a step of separating a tissue sheet from a material as    recited in (39) above, and a step of bonding a thermoplastic polymer    film to the peeled surface of said separated thin sheet.-   (43) A method of preparing a heat-sensitive stencil printing master,    comprising separating, from said material as recited in (40) above,    a laminate having the thin, sheet to which said thermoplastic    polymer film has been bonded.

BEST MODE FOR CARRYING OUT THE INVENTION

One embodiment of the multi-layer paper according to the presentinvention is a paper including at least two paper layers prepared andunified by a paper making method, wherein the multi-layer paper has atleast one peelable paper layer interface and is peelable into at leasttwo tissue sheets at the interface. Such a multi-layer paper will behereinafter referred to as Multi-layer Paper A.

The number of the paper layer of Multi-layer Paper A is not specificallylimited as long as it is at least two. The number is generally 2-5. Thenumber of the peelable interface is at least one, generally 1-4,preferably 1-2. Each of the paper layers of Multi-layer Paper A has abasis weight of 1-20 g/m², preferably 2-20 g/m². The basis weight ofrespective paper layers may be the same or may be different.

Multi-layer Paper A is delaminated at the peelable paper layer interface(hereinafter also referred to simply as peelable interface) to givetissue sheets corresponding in number to the number of the peelableinterface. When the number of the peelable interface is n, the number Nof the tissue sheets delaminated from one multi-layer paper is n+1,namely N=+1.

The tissue sheets obtained by delamination of Multi-layer Paper A may becomposed of one layer or a plural layers, generally 2-4 layers. WhenMulti-layer Paper A having n-number peelable interface is delaminated,(n+1)-number of tissue sheets can be obtained simultaneously.Alternatively, one delamination procedure can give two tissue sheets andeach tissue may be successively delaminated finally into (n+1)-number oftissue sheets.

In one preferred embodiment, Multi-layer Paper A is a 2-layer paperpeelable at the paper layer interface. The multi-layer paper (2-layerpaper) has a basis weight of 3-40 g/m², preferably 5-20 g/m². The2-layer paper gives two tissue sheets (hereinafter also referred to astissue papers) each of which is a single-layer sheet and at least one ofwhich has a basis weight of 1-20 g/m², preferably 2-10 g/m². Such a lowbasis weight tissue sheet may be suitably used as a porous support for apolymer film of a heat-sensitive stencil printing master.

In another preferred embodiment, Multi-layer Paper A is a 3-layer paperhaving two peelable interfaces. The multi-layer paper (3-layer paper)has a basis weight of 4-60 g/m², preferably 8-30 g/m². Each of the threetissue sheets is a single-layer sheet and at least one of them has abasis weight of 1-20 g/m², preferably 2-10 g/m².

In a further preferred embodiment, Multi-layer Paper A is a 3-layerpaper having one peelable interface at which delamination occurs. One ofthe two tissue sheets is a single-layer sheet, while the other tissuesheet is a two-layer sheet having a basis weight of 3-40 g/m²,preferably 5-20 g/m².

Each of the paper layers constituting Multi-layer Paper A may be formedof organic fibers or inorganic fibers. Examples of the organic fibersinclude natural fibers such as cellulose fibers and protein fibers,semisynthetic or reclaimed fibers such as rayon fibers and Lyocellfibers, and synthetic fibers such as polyolefin fibers, polyesterfibers, nylon fibers and acrylonitrile fibers. Examples of the inorganicfibers include carbon fibers, glass fibers and alumina fibers. Theorganic and inorganic fibers have a diameter of 1-40 μm, preferably 3-20μm, and a length of 1-15 mm, preferably 2-10 mm.

The above-described fibers constituting each paper layer may be amixture of various kinds of the above fibers. When two or more kinds offibers are used as a mixture, the kinds of the fibers and the mixingratio thereof may be suitably determined according to the intended useof the tissue sheets delaminated from the multi-layer paper.

Each of the paper layers constituting Multi-layer Paper A generally hasan intralayer peel strength of greater than 10 N/m, preferably at least20 N/m.

The peelable interface of Multi-layer Paper A generally has a peelstrength of 10 N/m or less, preferably 6 N/m or less. The lower limit ofthe peel strength is not specifically limited. A peel strength of thepeelable interface more than 10 N/m but no more than 20 N/m is likely tocause partial intralayer destruction upon delamination. Delamination isimpossible when the peel strength is more than 20 N/m. When the peelstrength is at least 0.5 N/m, the multi-layer paper can be handled as anintegrated state without being peeled in the interface up to until thedelamination has been conducted.

Because of its very low peel strength of 10 N/m or less and excellentpeelability, Multi-layer Paper A can give high grade, delaminated tissuesheets free of partial destruction even though the low basis weight andthe density are low.

It is preferred that the two adjacent paper layers between the peelableinterface of Multi-layer Paper A be such a combination in which affinitytherebetween is low for reasons of high peelability. Examples ofcombinations include a combination of a layer of cellulose fibers with alayer of synthetic fibers, such as polyester fibers, vinylon fibers,nylon fibers, acrylonitrile fibers or polyolefin fibers; a combinationof a layer of polyolefin fibers with a layer of heteroatom (e.g. oxygenor nitrogen)-containing synthetic fibers such as polyester fibers,vinylon fibers, nylon fibers or acrylonitrile fibers. For the purpose ofthe present invention, a combination of a cellulose fiber-based layerwith a synthetic fiber-based layer or a combination of apolyolefin-based layer with a polyester fiber-based layer is preferred.Especially preferred combination is a combination of a cellulosefiber-based layer with a polyester fiber-based layer. The cohesive forceof a cellulose fiber layer is mainly attributed to hydrogen bondingbetween fibers, whereas that of a synthetic fiber layer is mainlyattributed to adhesion between fibers through binder fibers. These paperlayers have sufficient strengths. Because of poor affinity between thefibers constituting the layers, the peel strength is low so that theyare easy to separate.

As the fibers constituting the cellulose fiber paper layer, anyconventionally employed pulp fibers, such as wood pulp fibers or papermaking pulp fibers, may be used. For reasons of low peel resistance andsuitable functions for tissue paper, the use of fibers conventionallyused for low density tissue paper is preferred. The use of naturalfibers of, for example, kozo, mitsumata, flax, Manila hemp or sisal, ispreferred. Manila hemp and sisal are easily feasible and suitably used.The natural fibers are desirably not heavily beaten.

The cellulose fibers may be cellulose fiber-based fibers and may beadded with other fibers such as semi-synthetic fibers e.g. rayon fibersor Lyocell fibers. Further, the cellulose fibers may be blended withsynthetic fibers, such as vinylon fibers, polyacrylonitrile fibers orpolyester fibers, in an amount of not greater than 10 mass %, as long asthe blend does not adversely affect the objects of the presentinvention. Further, the cellulose fibers may be blended with binderfibers, such as composite fibers having a core-sheath structure whosesurfaces are softened at the time of drying their wet paper or polyvinylalcohol fibers whose surfaces are fusible with hot water, in an amountof not greater than 10 mass %. Additionally, the cellulose fiber-basedlayer may contain a sizing agent, a dry or wet paper strength additive,a dispersing agent, an anti-foaming agent, an antistatic agent and otherchemicals for use in paper making.

It is preferred that the cellulose fiber-based layer contain a releasingagent for reasons of reduction of peel resistance in the interface. Thereleasing agent may be a conventionally employed wax such aspolyethylene wax or a higher fatty acid ester. The amount of thereleasing agent is such as not to adversely affect the usage of tissuepapers. For example, in the case of a heat-sensitive stencil printingmaster, the amount of the releasing agent is such as not to adverselyaffect the lamination with a thermoplastic resin film. Other chemicalshaving an effect as a releasing agent, such as an alkyl ketene dimersizing agent, may be suitably used as the releasing agent.

The synthetic fiber-based layer may be a layer containing syntheticfibers as major component. Various synthetic fibers may be suitablyselected according to the functions required for tissue papers obtainedby delamination. Various kinds of synthetic fibers conventionallyemployed for the formation of paper may be used. The synthetic fibersmay be, for example, heteroatom-containing synthetic fibers such asvinylon fibers, polyacrylonitrile fibers, polyamide fibers or polyesterfibers; or polyolefin fibers. Composite binder fibers are composed of ahigh melting point component and a low melting point component and aregenerally named using the resin of the high melting point component.Thus, composite binder fibers containing heteroatom-containing syntheticfibers or polyolefin fibers as the high melting point component thereofmay be termed as heteroatom-containing resin composite binder fibers andpolyolefin composite binder fibers, respectively. Also, paper layers inthe present invention are referred to herein in terms of the majorfibers constituting the paper layer and in terms of the resin of thehigh melting point component of the binder fibers constituting the paperlayer. For example, there is herein called a polyolefin-based layer orpaper layer.

As the synthetic fibers, heteroatom-containing synthetic fibers such aspolyester fibers are suitably used. When a tissue sheet of syntheticfibers obtained by delamination is intended to be used as a material forpreparing a heat-sensitive stencil printing master, it is preferred thatthe synthetic fibers have a fineness of. 0.1-2.2 dtex and a length of 15mm or less, more preferably 10 mm or less, most preferably 5 mm or less.The lower limit of the fiber length is generally about 1 mm. Thesynthetic fiber-based layer may contain semi-synthetic fibers, such asrayon or Lyocell, or cellulose fibers, such as Manila hemp or sisal, inan amount of 10% by weight or less. Additionally, the syntheticfiber-based layer may contain a paper strength additive, a dispersingagent, an anti-foaming agent, an antistatic agent and other chemicalsfor use in paper making.

The synthetic fiber-based layer used in the present invention has abasis weight of 1-20 g/m², preferably 2-10 g/m², and a density of 0.40g/cm³ or less, preferably 0.35 g/cm³ or less, more preferably 0.25 g/cm³or less. The lower limit of the density is generally 0.10 g/cm³.

The peelability of the interface also depends upon the sectional shapeof the fibers of the each paper layer. In the case of any of thecellulose fibers, synthetic fibers and semisynthetic fibers, the peelstrength of the interface decreases as the sectional shape of the fiberbecomes rounder, because the number of contact points and the area ofcontact between the fibers decrease. For example, the peel strength ofthe interface between a Manila hemp fiber layer and a polyester fiberlayer of a multi-layer paper obtained by unifying them by a paper makingmethod using a TAPPI standard sheet machine, was 2.1 N/m. When flat,softwood kraft pulp (NBKP) fibers were substituted for the Manila hempfibers, the peel strength was 3.6 N/m and greater than that of theManila hemp fibers. Since a mercerization treatment can round thesectional shape of cellulose fibers in a small degree, the use ofmercerized cellulose fibers can decrease the peel resistance of theinterface.

A peel strength of 10 N/m or less may be obtained even in the case of amulti-layer paper comprised of non-oriented fiber layers made byunification by paper making using a TAPPI standard sheet machine.However, it is preferred that the adjacent two paper layers defining theinterface be a combination of a high oriented fiber layer and a loworiented fiber layer, because the contact points and contact areabetween fibers in the paper layer interface decrease and because thepeel resistance in the paper layer interface decreases. In terms of“degree of fiber orientation” which is defined as a ratio of the tensilestrength in the machine direction to the tensile strength in the crossdirection, it is preferred that a difference in degree of fiberorientation between the adjacent two layers be at least 3, morepreferably at least 5. The upper limit of the difference is generally 8.In the case of unification by paper making of a combination of paperlayers both of which have a high degree of fiber orientation, it isdifficult to obtain a peel strength of 10 N/m or less. It is alsodifficult to uniformly delaminate them in the cross direction. Except aroll former (rote former) which can provide a very low degree of fiberorientation, a cylinder machine provides a paper making method producinga high degree of fiber orientation of 6 or more. A Fourdrinier machineor a short wire machine can generally provide a slightly less degree oforientation of 3-5. An inclined-wire machine can produce a paper havinga wide degree of orientation of from less than 1 up to a comparabledegree to the cylinder machine but is characterized in that it canprovide a degree of fiber orientation of 2 or less.

Multi-layer Paper A of the present invention may be obtained by aconventional paper making method in which at least two wet embryoniclayers are combined together and thereafter dried. Each of the wetlayers corresponds to each of the paper layers constituting Multi-layerPaper A. A wet paper layer may be formed from a fiber-containingmaterial. The fibers contained in the material may be suitably selectedaccording to the desired constitution of the multi-layer paper. Inaddition to fibers, the stock may contain a sizing agent, a paperstrength additive, a dispersing agent, an anti-foaming agent, anantistatic agent and other paper making chemicals, as necessary. As apaper machine, there may be used any suitable known paper machine suchas a cylinder machine, an inclined-wire machine, a Fourdrinier machineor a short wire machine.

In the paper making method employed for the purpose of the presentinvention, two or more wet layers providing peelable interface orinterfaces are combined and unified together. Suitable examples of theprocess for the unification include (i) combining a wet synthetic fiberlayer formed using a cylinder machine with a wet cellulose fiber layerformed using an inclined-wire machine, (ii) combining a wet syntheticfiber layer formed using a cylinder machine with a wet cellulose fiberlayer formed using an inclined-wire machine and with a wet syntheticfiber layer formed using a cylinder machine, and (iii) combining a wetsynthetic fiber layer formed using an inclined-wire machine with a wetcellulose fiber layer formed using a cylinder machine and with a wetsynthetic fiber layer formed using an inclined-wire machine.

To reduce the peel resistance in the interface at which two layers arecombined, it is important to reduce entanglement of fibers between thetwo layers. Thus, it is preferred that at least one of the two surfacesof the two layers, which surfaces are to form the interface therebetweenbe subjected to a smoothing treatment for reasons of reducing the peelresistance. The smoothing treatment may include pressing a surface of arunning wet layer supported on a felt with, for example, a wire roll sothat those parts of fibers protruding from the surface are pressed downor the surface is smoothed. A multi-layer paper obtained using such asurface-smoothed layer contains a paper layer which corresponds to thewet layer and whose surface is smoothed. Namely, in the interfacebetween the surface-smoothed paper layer and another layer, the contactpoints and contact area between the fibers of respective layers arereduced. Therefore, the peel resistance in the interface can be reduced.As a result, it is possible to obtain an interface whose peel strengthis reduced to 10 N/m or less.

A further effective method to obtain a peelable interface is a method inwhich a releasing agent is incorporated into at least one of twoadjacent layers to be combined. By adding the releasing agent to astock, the releasing agent can be incorporated into the wet paper layer.The amount of the releasing agent may vary according to the intended useof the multi-layer paper produced. Generally, the releasing agent isused in an amount of 0.01-1.5 parts by mass (solid matter), preferably0.1-1.0 part by mass, per 100 parts by weight of the fibers.

A further effective method of obtaining a peelable interface is a methodin which one of the adjacent two layers is imparted with a higher degreeof fiber orientation than the other is. In terms of “degree of fiberorientation” which is defined as a ratio of the tensile strength in themachine direction to the tensile strength in the cross direction, it ispreferred that a difference in degree of fiber orientation between thehigh oriented fiber layer and the low oriented fiber layer be at least3, more preferably at least 5. A high orientation can be obtained byusing a cylinder machine which can provide a high degree of fiberorientation of 6 or more. A Fourdrinier machine or a short wire machinecan produce a paper layer having a degree of orientation of 3-5. With aninclined-wire machine, a paper layer having a degree of fiberorientation of 2 or less may be prepared.

As will be understood from the above description, it is preferred that amethod be adopted in which a wet web formed by a cylinder machine iscombined with a wet web formed by an inclined-wire machine for thepurpose of obtaining a multi-layer paper having highly peelableinterface.

A further effective method of improving the peelability of the interfaceat which two layers are combined is to decrease the density of amulti-layer paper by reducing a pressure at which the two wet layers arecombined or at which the combined wet layers is pressed for dewartering,or by reducing a touch pressure at which the combined layers arecontacted with a dryer.

In Multi-layer Paper A according to the present invention, the paperlayer composed mainly of synthetic fibers (synthetic fiber paper layer)contain binder fibers. When the synthetic fiber layer is combined withanother paper layer, for example a paper layer composed mainly ofcellulose fibers (cellulose fiber paper layer), and when the combinedlayers are heated with a drier for drying, the surfaces of the binderfiber are fused so that the fibers are bonded together to give a paperlayer having an increased strength. In the case of drying combined paperlayers, when the drying temperature is high, the peel strength of theinterface increases so that the peelability tends to be poor. Thus, itis important that the drying temperature be suitably controlled from thestandpoint of both destruction strength of the paper layer and the peelstrength of the interface. Such a temperature control is important whena Yankee drier which heats a multi-layer sheet from one side is used.

The binder fibers used in the present invention exhibit a binding effectat a drying temperature at which unified multi-layer wet web is dried.In this case, the drying temperature is a temperature to which the wetweb is exposed during the drying step and is generally 90-120° C.,preferably 90-110° C. Thus, any binder fibers may be used for thepurpose of the present invention, as long as they can exhibit the bindereffect at 90-120° C., preferably 90-110° C. The binder effect of thebinder fibers is ascribed to adhesive softened components produced bysoftening part of the binder fibers when heated to the abovetemperature.

The resin component exhibiting its binder effect at the abovetemperature is a non-crystalline polymer or copolymer which is softenedor melted at a temperature in the above range. Examples of such polymersor copolymers include polyester resins such as copolyesters (low meltingpoint PET); polyolefin resins such as modified polyethylene (low meltingpoint PE), polyethylene (PE) and modified polypropylene (low meltingpoint PP); ethylene/vinyl acetate copolymers (EVA); copolymerized nylon;and polyvinyl alcohol (PVA) by hot water fusion.

The binder fibers include composite fibers and single-component fibers.Composite fibers are composed of a high melting point component and alow melting point component. The composite fibers may be of aside-by-side type or a core-sheath type. The side-by-side type fibersmay be, for example, PET-low melting point PET fibers or PP-PE fibers.The core-sheath type fibers may be, for example, PET-low melting pointPET fibers, PET-PE fibers, PET-low melting PP fibers, PP-low meltingpoint PE fibers, PP-PE fibers, PET-low melting point PP fibers, nylon66-nylon 6 fibers or PP-EVA fibers. The single-component fibers may be,for example, low melting point PET (copolyester) fibers, low meltingpoint PP fibers, PE fibers or PVA fibers. In the present invention, anyfibers may be used as the binder fibers as long as the fibers canexhibit the binding effect at the above temperature. Especially suitablebinder fibers are PET-low melting point PET fibers which are polyestercomposite fibers having a so-called core-sheath structure. Theproportion of the sheath component which is a low melting pointcomponent of the composite fibers of a core-sheath structure isgenerally 40-70 mass %. The copolyester of the sheath component of thecomposite fibers does not show a clear melting point but is softened ormelted at the above-described drying temperature. Such a temperature canbe measured by naked eyes through microscopic observation as atemperature at which surfaces of the fibers are melted at intersects andis referred to as fusion temperature or binding temperature.

The fineness of the binder fibers is preferably 0.1-2.2 dtex and thelength thereof is 15 mm or less, preferably 10 mm or less, morepreferably 5 mm or less.

Various kinds of binder fibers are commercially available and they canbe used for the purpose of the present invention. Examples ofcore-sheath type composite fibers composed of a high melting point corecomponent and a low melting point sheath component include PET-lowmelting point PET fibers such as SOFIT (R) N720, SOFIT (R) N720H bothmanufactured by Kuraray Co., Ltd., MELTY 4080 manufactured by UnitikaLtd., TJ04CN manufactured by Teijin Ltd., NBF(SH) manufactured byDaiwabo Co., Ltd. and ETC manufactured by Chisso Corporation;PET-modified PP fibers such as NBF(SP) manufactured by Daiwabo Co.,Ltd.; PP-low melting point PE fibers such as EAC manufactured by ChissoCorporation; PP-PE fibers such as NBF(H) manufactured by Daiwabo Co.,Ltd. and ESC manufactured by Chisso Corporation; and PP-EVA fibers suchas NBF(E) manufactured by Daiwabo Co., Ltd. Examples of side-by-sidetype composite fibers composed of a high melting point core componentand a low melting point sheath component include PET-low melting pointPET fibers such as SOFIT (R) N784 manufactured by Kuraray Co., Ltd.;PP-low melting point PE fibers such as EA manufactured by ChissoCorporation; and PP-PE fibers such as ES manufactured by ChissoCorporation. MELTY(R)4000 manufactured by Unitika Ltd. is an example ofa single-component binder fibers composed only of a low melting pointcomponent. As PVA fibers, there may be mentioned VPB101, VPB105-1,VPB105-2 all manufactured by Kuraray Co., Ltd., and SMM, SML and SMSmanufactured by Unitika Ltd.

In Multi-layer Paper A according to the present invention, at least apart of the synthetic fibers contained in the synthetic fiber paperlayer are binder fibers. The amount of the binder fibers contained inthe synthetic fibers is 20-100 mass %, preferably at least 30 mass %,more preferably at least 40 mass %, in the case of composite binderfibers. In the case of a single-component binder fibers, the amount is20-70 mass %, preferably 60 mass % or less, more preferably 50 mass %.

In one preferred combination of adjacent two paper layers of Multi-layerPaper A, one paper layer contains heteroatom-containing synthetic resinfibers as a high melting point component that is not softened or meltedat the drying temperature of 90-120° C., while the other paper layercontains polyolefin resin fibers as a high melting point component. Inthis case, as a resin component which exhibits the binder effect, namelyas a low melting point sheath component of the composite binder fibersor as a resin component of the single-component binder resin, it ispreferred that a low melting point polyester resin be used in the onelayer containing the heteroatom-containing synthetic resin fibers andthat a low melting point polyolefin resin or an ethylene/vinyl acetatecopolymer be used in the other paper layer containing the polyolefinresin fibers.

The binder fibers used in a layer containing heteroatom-containingsynthetic resin fibers may be composite fibers composed of a sheathcomponent of a low melting point polyester resin and a core component ofa heteroatom-containing synthetic resin or a high melting pointpolyolefin resin. As single-component binder fibers, there may be usedlow melting point polyester fibers. The use of the former compositebinder fibers is preferable for reasons of good peelability when theadjacent paper layer is a cellulose fiber-based layer or a polyolefinfiber-based layer containing a low melting point polyolefin resin or anethylene-vinyl acetate copolymer as a binder resin component.

The binder fibers used in a layer containing polyolefin fiberspreferably contain a binder resin component of a low melting pointpolyolefin resin or an ethylene/vinyl acetate copolymer. In this case,good peelability may be obtained when the adjacent paper layer is acellulose fiber-based layer or a layer containing a low melting pointpolyester resin as its binder resin component. As the binder fibers, itis preferable to use composite binder fibers composed of a low meltingpoint polyolefin resin or an ethylene/vinyl acetate copolymer as asheath component, and a high melting point polyolefin resin such as apolypropylene resin or a heteroatom-containing synthetic resin as a corecomponent.

The heteroatom-containing synthetic fibers are those made of a syntheticresin containing a heteroatom (e.g. oxygen or nitrogen) such aspolyester, polyamide, polyacrylate and polyacrylonitrile.

In Multi-layer Paper A according to the present invention in which eachof the adjacent paper layers defining the peelable interfacetherebetween is made of synthetic resin fibers, it is possible to reducethe peel strength of the peelable interface by using resins having lowaffinity with each other for the sheath components of the binder fibersto be incorporated into respective paper layers. For example, when oneof the two layers contains composite binder fibers containing apolyolefin resin or an ethylene/vinyl acetate copolymer as a resinconstituting the sheath, the other layer may be suitably contains binderfibers containing a polyester resin as a resin constituting the sheath.As a consequence of the above combination, the peel strength of theinterface can be reduced.

The production of Multi-layer Paper A will be described more concretelybelow.

-   (1) Preparation of Multi-layer Paper (I):

Using Manila hemp as cellulose fibers, two Manila hemp fiber layers wereprepared and combined with a TAPPI standard sheet machine and thendried. The delamination in the interface at which two layers werecombined caused partial breakage of the paper layers. The peelresistance was 14 N/m.

When the above procedures were repeated in the same manner as describedexcept that one of the wet furnish layer was smoothed with a rollerbefore combining with the other furnish layer, the peel strength of thetwo-layer paper was 9.8 N/m. The sheet was able to be uniformlyseparated at the interface therebetween.

The above paper layers were combined as follows. A layer of a furnishformed on a wire of the TAPPI standard sheet machine was contacted witha filter paper and picked up thereon. The wet furnish layer on thefilter paper was overlaid with another furnish layer formed on the TAPPIstandard sheet machine.

Separately, a wet furnish layer on a filter paper was dried in a hot airdrier at 70° C. for 1.5 hours. The dried surface of the hemp fiber layerwas fuzzy and had long 229 fuzzes per 100 cm². Another wet layer on afilter paper was subjected to a smoothing treatment and then dried. Thefuzzes on the smoothed surface were shorter and the number thereof was81 per 100 cm². The smoothing treatment was confirmed to be effective topress part of protruded fuzzes down into the wet layer.

-   (2) Preparation of Multi-layer Paper (II):

60 Mass % of non-stretched polyester fibers (TEPYRUS TKO8PN manufacturedby Teijin Ltd.) having a fineness of 0.2 dtex and a length of 3 mm weremixed with 40 mass % of polyester binder fiber (sheath component: lowmelting point PET, fusion temperature: 110° C.; core component: PET;SOFIT N720 manufactured by Kuraray Co., Ltd.) having a fineness of 1.7dtex and a length of 5 mm to obtain a stock. Using this stock, apolyester fiber layer was formed on a wire of a TAPPI standard sheetmachine in an amount corresponding to a basis weight of 2 g/m² and waspicked up on a filter paper. A Manila hemp pulp was beaten to CanadianStandard freeness (CSF) 550 to obtain a stock. Using this stock, aManila hemp fiber layer was formed on a wire of a TAPPI standard sheetmachine in an amount corresponding to a basis weight of 8 g/m². This wassuperimposed by picking up on the wet polyester fiber layer on thefilter paper. The resulting combined sheet was pressed for dewateringand dried on a cylindrical drier at 105° C. for experimental use toobtain a 2-layer paper (II) having a polyester fiber layer and a Manilahemp fiber layer. The peel strength of the 2-layer paper was found to be5.11 N/m in the combined interface. Delamination was uniformly occurredeven though the basis weight of the polyester fiber layer is as small as2 g/m². However, the polyester fiber tissue sheet thus obtained had atensile strength of 0.030 kN/m which was near the lower limit enablinglayer-layer separation.

-   (3) Preparation of Multi-layer Paper (III):

The procedures for the above multi-layer paper (II) were repeated in thesame manner as described except that the basis weight of the polyesterfiber layer was decreased to 1 g/m², thereby obtaining 2-layer paper(III). Due to internal destruction (breakage of the material) of thepolyester fiber layer, the 2-layer paper (III) was not able to bedelaminated at the interface.

-   (4) Preparation of Multi-layer Papers (IV) and (V):

The procedures for the above multi-layer paper (II) were repeated in thesame manner as described except that the basis weight of the polyesterfiber layer was increased to 5 g/m² and that the basis weight of thehemp fiber layer was decreased to 3 g/m² and 2 g/m², thereby obtaining2-layer papers (IV) and (V), respectively. The peel strength of the2-layer paper having the basis weight of the hemp fiber layer of 3 g/m²was found to be 2.92 N/m between the polyester fiber layer and the hempfiber layer. The hemp fiber tissue sheet thus obtained had a tensilestrength of 0.031 kN/m which was near the lower limit for providing asuitable basis weight of a tissue paper. In the case of the 2-layerpaper having the basis weight of the hemp fiber layer of 2 g/m², it wasdifficult to delaminate at the interface, because of breakage of theManila hemp fiber layer.

The basis weight of each of the layers of the multi-layer paper of thepresent invention varies with the function required for the tissue sheetobtained by the delamination and is not specifically limited. Forexample, when the tissue sheet is used as a porous substrate forheat-sensitive stencil printing masters, the basis weight is 1-20 g/m²,preferably 1-10 g/m², from the standpoint of the function required forthe porous substrate. A basis weight smaller than 1 g/m² results in lowstrength, whereas too large a basis weight in excess of 20 g/m²adversely affects the ink permeability.

In the case of 2-layer paper composed of a Manila hemp fiber layer and apolyester-fiber layer, it was found to be necessary that the basisweight of the Manila hemp fiber layer was at least 3 g/m² and the basisweight of the polyester fiber layer was at least 2 g/m² in order thateach of the layer had a tensile strength of at least 30 N/m whileensuring peelability at the interface. Therefore, when a single-layertissue sheet delaminated from a multi-layer paper is used for laminationwith a thermoplastic resin film, it is preferred that the basis weightthereof be at least 3 g/m² when the layer is a cellulose-based layer andat least 2 g/m² when the layer is a synthetic resin fiber-based layer.

When a single-layer tissue sheet is delaminated from a multi-layer paperafter a thermoplastic resin film has been bonded to the multi-layerpaper, the basis weight of the tissue sheet can be small, since thethermoplastic resin film bonded thereto serves as a strength impartingsupport. Thus, when the tissue sheet is used as a porous support, forexample, the basis weight thereof is preferably at least 1 g/m², morepreferably at least 2 g/m², for obtaining satisfactory ink permeability.

Also when a tissue sheet is delaminated from a multi-layer paper as alaminated sheet with another layer, such another layer serves tofunction as a strength imparting support. Thus, the basis weight of theone layer can be about 1 g/m².

-   (5) Preparation of Multi-layer Papers (VI)-(X):

60 Mass % of non-stretched polyester fibers (TEPYRUS TKO8PN manufacturedby Teijin Ltd.) having a fineness of 0.2 dtex and a length of 3 mm weremixed with 40 mass % of polyester binder fibers (sheath component: lowmelting point PET, fusion temperature: 110° C.; core component: PET;SOFIT N720 manufactured by Kuraray Co., Ltd.) having a fineness of 1.7dtex and a length of 5 mm to obtain a stock. Using this stock, apolyester fiber layer was formed on a wire of a TAPPI standard sheetmachine in an amount corresponding to a basis weight of 5 g/m² and waspicked up on a filter paper. A Manila hemp pulp was beaten to CanadianStandard freeness (CSF) 550 to obtain a stock. Using this stock, aManila hemp fiber layer was formed on a wire of a TAPPI standard sheetmachine in an amount corresponding to a basis weight of 8 g/m². This wassuperimposed by picking up on the wet polyester fiber layer on thefilter paper. The resulting combined sheet was pressed for dewateringand dried on a cylindrical drier having surface temperatures of 85° C.,90° C., 100° C., 105° C. and 110° C. to obtain 2-layer papers (VI)-(X),respectively. The peel strengths of the 2-layer papers (VII)-(VIII)obtained at drying temperatures of 90-105° C. ranged 1.76-1.97 N/m anddelamination at the interface was uniformly made. In the case of the2-layer paper (VI) obtained at a drying temperature of 85° C., breakageof the material of the polyester fiber layer occurred. In the case ofthe 2-layer paper (X) obtained at a drying temperature of 110° C.,delamination caused breakage of the sheet and considerable fuzzing sothat uniform delamination at the interface was not able to be made.Thus, the drying temperature for 2-layer paper composed of the polyesterfiber layer and the Manila hemp pulp layer in the range of 90-105° C.was found to be desirable. This range was lower by 5° C. than thebinding temperature of the binder fibers.

-   (6) Preparation of Multi-layer Paper (XI):

Using 100 mass % of polyester binder fibers (sheath component: lowmelting point PET, fusion temperature: 110° C.; core component: PET;MELTY 4080 manufactured by Unitika Ltd.) having a fineness of 1.7 dtexand a length of 5 mm as a stock, a polyester fiber layer was formed on awire of a TAPPI standard sheet machine in an amount corresponding to abasis weight of 15 g/m² and was picked up on a filter paper. Using 100mass % of polyolefin binder fibers (sheath component: low melting pointPE, fusion temperature: 110° C.; core component: PP; EAC manufactured byChisso Inc.) having a fineness of 2.2 dtex and a length of 5 mm as astock, a polyolefin fiber layer was formed on a wire of a TAPPI standardsheet machine in an amount corresponding to a basis weight of 15 g/m².This was superimposed by picking up on the wet polyester fiber layerpreviously picked up on the filter paper. The resulting combined sheetwas pressed for dewatering and dried on a cylindrical drier forexperimental use at 105° C. to obtain a 2-layer paper (XI) having apolyester fiber layer and a polyolefin fiber layer. The peel strength ofthe 2-layer paper was found to be 2.3 N/m in the combined interface.Delamination was uniformly occurred.

-   (7) Preparation of Multi-layer Paper (XII):

Using 100 mass % of polyester binder fibers (sheath component: lowmelting point PET, fusion temperature: 110° C.; core component: PET;MELTY 4080 manufactured by Unitika Ltd.) having a fineness of 1.7 dtexand a length of 5 mm as a stock, a polyester fiber layer was formed on awire of a TAPPI standard sheet machine in an amount corresponding to abasis weight of 15 g/m² and was picked up on a filter paper. Using 100mass % of binder fibers having ethylene/vinyl acetate as a sheathcomponent (fusion temperature: 100° C.; core component: PP; NBF(E)manufactured by Daiwabo Co., Ltd.) having a fineness of 2.2 dtex and alength of 5 mm as a stock, a binder fiber layer having a polyolefinresin core component was formed on a wire of a TAPPI standard sheetmachine in an amount corresponding to a basis weight of 15 g/m². Thiswas superimposed by picking up on the wet polyester fiber layerpreviously picked up on the filter paper. The resulting combined sheetwas pressed for dewatering and dried on a cylindrical drier forexperimental use at 105° C. to obtain a 2-layer paper (XII) having apolyester fiber layer and a polyolefin fiber layer. The peel strength ofthe 2-layer paper was found to be 7.8 N/m in the combined interface.Delamination was uniformly occurred.

-   (8) Preparation of Multi-layer Paper (XIII):

Using a Manila hemp pulp beaten to Canadian Standard freeness (CSF) 670as a stock, a Manila hemp fiber layer was formed on a wire of a TAPPIstandard sheet machine in an amount corresponding to a basis weight of20 g/m² and was picked up on a filter paper. Using 100 mass % ofpolyolefin binder fibers (sheath component: low melting point PE, fusiontemperature: 110° C.; core component: PP; EAC manufactured by ChissoInc.) having a fineness of 2.2 dtex and a length of 5 mm as a stock, apolyolefin fiber layer was formed on a wire of a TAPPI standard sheetmachine in an amount corresponding to a basis weight of 20 g/m². Thiswas superimposed by picking up on the wet Manila hemp fiber layerpreviously picked up on the filter paper. The resulting combined sheetwas pressed for dewatering and dried on a cylindrical drier forexperimental use at 105° C. to obtain a 2-layer paper (XIII) having apolyester fiber layer and a Manila hemp fiber layer. The peel strengthof the 2-layer paper was found to be 1.2 N/m in the combined interface.Delamination was uniformly occurred.

From the above results, for the production of a multi-layer paper havingan interface having an interlayer peel strength of 10 N/m or less andshowing good peelability, it is preferred that the drying temperaturefor the combined wet embryonic layers be lower by 5-20° C., morepreferably 5-10° C., than the binder effect exhibition temperature ofthe binder fibers incorporated in the synthetic fiber-based layer.

In the production of Multi-layer Paper A in the manner described above,a surface of the multi-layer paper obtained from the unifying step bypaper making method may be applied with a surface coating agent forpaper making, if desired. In the case of a multi-layer paper composed ofa layer composed mainly of cellulose fibers and unified with a layercomposed mainly of synthetic fibers, a coating liquid containing starchor polyvinyl alcohol which is low in affinity with the synthetic fiberscan improve the intralayer cohesive strength of the cellulosefiber-based layer and prevent fuzz and falling off of cellulose fiberswithout adversely affecting the peelability at the interface at whichtwo layers are combined and is preferably used.

One of the most preferred construction of Multi-layer Paper A which hasan interface having an interlayer peel strength of 10 N/m or less andwhich exhibits good peelablity uses a combination of a polyester fiberlayer with a Manila hemp fiber layer. Fiber compositions of each of thefiber layers will be next described in more detail.

As described previously, Manila hemp fibers are most preferably used asthe cellulose fibers. Manila hemp fibers beaten to provide CSF 550-730are suitably used. The hemp fiber layer can contain semi-syntheticfibers such as rayon. When a tissue sheet formed of the hemp fibers isused as a porous support of a heat-sensitive stencil printing master, itis preferred that the hemp fiber layer contain a synthetic fibers, suchas stretched polyester, vinylon or polyacrylonitrile, for reasons ofimproved dimensional stability against temperature changes of thestencil master. Because of a reduction of intralayer cohesive strengthand resulting increase of dropping off of fibers, however, the amount ofthe synthetic fiber in the hemp fiber layer should be preferably notgreater than 10% by weight. The hemp fiber layer can also contain binderfibers such as polyvinyl alcohol fibrous binder or binder fibers of acore-sheath structure capable of forming interfiber bonding by fusebonding at fiber surfaces. The amount of the binder fibers should bepreferably not greater than 10% by weight for reasons of the peelresistance.

As the polyester fiber used in the polyester fiber layer, there may beused a mixture of composite polyester fibers having fusible surfaces(generally called binder fibers) with stretched polyester fibers and/ornon-stretched polyester fibers. These fibers are suitably selected fromthose having a diameter of 0.1-2.2 dtex. The binder fibers, which arepreferably composite polyester fibers having a core-sheath structure,are preferably contained in the polyester fiber layer in an amount of20-100 mass %. An amount of the binder fibers below 20 mass % fails toprovide sufficient intralayer cohesive strength of the polyester fiberlayer. The blending ratio, fiber diameter and fiber length of thestretched and non-stretched polyester fibers are suitably selected withthe consideration of falling off of fibers and required function such asphysical properties thereof which influence upon the image grade whenused for a heat-sensitive stencil printing master. The stretched andnon-stretched polyester fibers are preferably contained in the polyesterfiber layer in an amount of 0-80 mass % in total. With regard to theblending ratio, the non-stretched polyester fibers, which exhibit a weakbinding force at ordinary drying temperature and are effective inprevention of fuzz on a peeled surface and of falling off of fibers, arepreferably used in an amount of 0-80 mass %. The stretched polyesterfibers, which have no binding force and cause falling off of fibers froma peeled surface, are preferably used in an amount of 0-20 mass %. Thelength of the polyester fibers is 15 mm or less, preferably 10 mm orless, most preferably 5 mm or less, for reasons of dispersibility andtexture.

In another embodiment of the present invention, there is provided amulti-layer paper comprising at least three paper layers each having abasis weight of 1-20 g/m². The multi-layer paper has, as an intermediatelayer, at least one paper layer at which intralayer delamination canoccur and at which the multi-layer paper is peelable into at least twotissue sheets. The multi-layer paper will be hereinafter referred to as“Multi-layer Paper B”.

Multi-layer Paper B is peelable in the intralayer-delaminatableintermediate layer (hereinafter also referred simply to as “intermediatelayer” to give tissue sheets of a number which is greater by 1 than thenumber of the intermediate layer.

The tissue sheets obtained by the delamination of Multi-layer Paper Bmay include a paper layer and an approximately half of the intermediatelayer, or a plurality of paper layers and an approximately half of theintermediate layer. The number of the paper layers constitutingMulti-layer Paper B is at least 3 inclusive of the number of theintermediate layer. The number of the intermediate layer is smaller by 1than the number of the desired tissue sheets and is generally 1-3,preferably 1-2. The basis weight of each of the paper layers is suitablydetermined according to the intended use thereof and is generally 1-20g/m², preferably 1-10 g/m². The basis weight of the paper layers otherthan the intermediate layer may be the same or different.

The peel strength of the paper layer interface of Multi-layer Paper B isgenerally greater than 10 N/m, preferably at least 20 N/m.

The intralayer peel strength of the intermediate layer is lower thanthat of the interface and is generally 10 N/m or less, preferably 6 N/mor less. The lower limit of the peel strength is about 0.5 N/m.

The intermediate layer may-be a paper layer composed mainly of cellulosefibers or a paper layer composed mainly of synthetic fibers.

In the case of the synthetic fiber-based intermediate paper layer, anysynthetic fibers may be used without limitation because synthetic fibershardly cause entanglement or binding between fibers. Synthetic fibersconventionally used as a porous support for a heat-sensitive stencilprinting master, such as vinylon fibers, polyacrylonitrile fibers,polyamide fibers or polyester fibers may be used. Above all, the use ofpolyester fibers is preferred. The polyester fibers are preferablystretched fibers to which at least 10 mass % of non-stretched fibers aremixed. In order to prevent the intermediate layer from delaminatinguntil up to a forced delamination step, it is necessary that at least 10mass % of non-stretched fibers which have weak bonding force be used.The fiber length is preferably as short as possible. Especiallypreferred is the fiber length of 3 mm or less. The peel strength of theintermediate layer is such that delamination of the multi-layer paper atthe intermediate layer does not easily occur during handling thereof.

The basis weight of the intermediate layer of synthetic fibers such aspolyester fibers is generally 2-8 g/m², preferably 2-6 g/m², morepreferably 2-4 g/m².

In the case of the cellulose fiber-based intermediate paper layer, theuse of semi-synthetic fibers e.g. rayon fibers or Lyocell fibers ormercerized Manila hemp fibers or hardwood pulp fibers is preferable forreasons of reduced entanglement or binding between fibers. When ordinaryManila hemp fibers which have not been subjected to a mercerizationtreatment are used, it is desired that the pulp fiber be not subjectedto a beating treatment but be only subjected to disintegration. Thefiber length is preferably as short as possible. Especially preferred isthe fiber length of 2 mm or less. It is preferred that the intermediatelayer composed mainly of cellulose fibers contain a releasing agent.

The basis weight of the intermediate layer of cellulose fibers isgenerally 5-10 g/m², preferably 5-8 g/m², more preferably 5-6 g/m².

In order to increase the bonding strength in the interface between theintermediate layer and each adjacent layer, it is necessary toincorporate fibers exhibiting high binder function into each adjacentlayer and to provide the binding force in the interface. It is preferredthat the binder fibers incorporated into each adjacent layer have highaffinity with the fibers of the intermediate layer. For example, whenthe intermediate layer is composed mainly of polyester fibers, thebinder fibers incorporated into each adjacent layer are preferablypolyester composite fibers. When the layers adjacent to the intermediatelayer are composed mainly of cellulose fibers, the use of polyvinylalcohol fibrous binder is generally preferred for reasons of highbonding strengths. However, for use in heat-sensitive stencil printingmasters, the use of polyester composite fibers is preferable for reasonsof resolution. The use of heat-fusible composite fibers such aspolyester composite fibers is preferred, since the bonding strength inthe interface increases when the combined sheet is dried at atemperature of the fusion temperature or higher. When the intermediatelayer is formed of polyester fibers and its adjacent layers are composedmainly of cellulose fibers, it is possible to increase the peel strengthin the interface by incorporating polyester composite fibers in thecellulose-fiber based paper layer and by drying at a temperature higherthan the fusion temperature thereof. The length of the binder fibers ispreferably large, because the greater the length of the binder fibers,the higher becomes the bonding strength at the interface.

The thickness of the intermediate layer is not desired to be excessivelylarge or small, but is desired to be in a suitable range. Although theintralayer peel resistance becomes low with an increase of the thicknessof the intermediate layer, too large a thickness thereof is undesirablebecause the intralayer delamination occurs at various location so thatthe thickness of the delaminated layers becomes undesirably non-uniform.Too small a thickness, on the other hand, causes an increase of the peelresistance in the intermediate layer and the intralayer delaminationcannot occur, because the binding force of the binder fibers containedin the adjacent layers reaches inside of the intermediate layer. Thediameter of the fibers of the intermediate layer is preferably small,because the smaller the diameter of the fibers, the less becomes theinfluence of the binding force of the binder fibers contained in theadjacent layers and, hence, the thickness of the intermediate layer canbe reduced.

The binder fibers incorporated into the paper layers adjacent to theintermediate layer exhibit the binder effect at the previously describeddrying temperature. When the adjacent layers are composed of syntheticfibers, the amount of the binder fibers incorporated into the syntheticfibers is 20-100 mass %, preferably at least 30 mass %, more preferablyat least 40 mass %, in the case of composite binder fibers. In the caseof single-component binder fibers, the amount is 20-70 mass %,preferably 60 mass % or less, more preferably 50 mass % or less.

The composite binder fibers and single-component binder fibers can bethose described above with reference to Multi-layer Paper A.

Multi-layer Paper B is preferably a 3-layer paper in which intralayerdelamination occurs in the intermediate layer. Such a multi-layer paper(3-layer paper) has a basis weight of 4-40 g/m², preferably 4-20 g/m².In this case, each of two tissue sheets (tissue papers) obtainedtherefrom by intralayer delamination is composed of one layer and thenearly halved intermediate layer and has a basis weight of 2-20 g/m²,preferably 3-10 g/m². Such small basis weight tissue sheets are suitablyused as a support for a thermoplastic resin film of a heat-sensitivestencil printing master.

Multi-layer Paper B is also preferably a 4-layer paper in whichintralayer delamination occurs in the second or third paper layer(intermediate layer). Such a multi-layer paper (4-layer paper) has abasis weight of 5-70 g/m², preferably 6-40 g/m². In this case, one oftwo tissue sheets obtained therefrom by intralayer delamination iscomposed of one layer and the nearly halved intermediate layer, whilethe other tissue sheet is composed of two paper layers and theintermediate layer divided nearly into halves. The former tissue sheethas a basis weight of 2-25 g/m², preferably 2-15 g/m², while the lattertissue sheet has a basis weight of 3-45 g/m², preferably 4-25 g/m² andis easy to handle because of its stiffness. In the latter tissue paper,one of the two layers other than the nearly halved intermediate layerserves to function as a support for reinforcing the whole tissue sheet.

Multi-layer Paper B is also preferably a 5-layer paper in whichintralayer delamination occurs in one of the second, third and fourthpaper layers (intermediate layer) or in each of the second and fourthpaper layers. Such a multi-layer paper (5-layer paper) has a basisweight of 6-80 g/m², preferably 7-30 g/m². In this case, two, first andsecond tissue sheets may be obtained by intralayer delamination at thesecond layer. The first tissue sheet is composed of the first paperlayer and the nearly halved second paper layer, while the second tissuesheet is composed of the third, fourth and fifth paper layers and thenearly halved second paper layer. Also, by intralayer delamination atthe third layer of the 5-layer paper, there can be obtained two, firstand second tissue sheets each composed of two paper layers and nearlyhalved third layer. Further, two, first and second tissue sheets may beobtained by intralayer delamination at the fourth layer. The firsttissue sheet is composed of the first, second and third paper layers andthe nearly halved fourth paper layer, while the second tissue sheet iscomposed of the fifth paper layer and the neatly halved fourth paperlayer. Further, three, first, second and third tissue sheets may beobtained by intralayer delamination at the second and fourth layers. Thefirst tissue sheet is composed of the first paper layer and the nearlyhalved second paper layer, and third tissue sheet is composed of thefifth paper layer and the nearly halved fourth paper layer. The secondtissue sheet is composed of the third paper layer and the nearly halvedsecond and fourth paper layers.

Multi-layer Paper B may be prepared by the conventional paper makingmethod similar to Multi-layer Paper A. In the paper making method, atleast three wet paper layers are combined and then dried forunification. The wet layers correspond to respective paper layersconstituting Multi-layer Paper B.

The production of Multi-layer Paper B will be described more concretelybelow.

(I) Preparation of Multi-Layer Paper Having Intermediate Layer IncludingManila Hemp Fibers:

A slurry as a stock for the intermediate layer was prepared bydisintegrating a Manila hemp pulp sheet without beating (average fiberlength: 4.3 mm). Also prepared was a slurry as a stock for theintermediate layer by cutting a Manila hemp pulp sheet with a razor intosmall squares of about 1 mm side length, followed by disintegration(average fiber length: 1.3 mm). As a stock for forming first and thirdlayers to be disposed adjacent to the intermediate layer, also preparedwas a slurry containing 60 mass % of non-stretched polyester fibers(TK08PN manufactured by Teijin Ltd.) having a fineness of 0.2 dtex and alength of 3 mm and 40 mass % of polyester binder fibers (sheathcomponent: low melting point PET, fusing temperature: 110° C.; corecomponent: PET; MELTY 4080 manufactured by Unitika Ltd.) having afineness of 1.7 dtex and a length of 5 mm, to which an acrylamide-typedispersing agent (ACRYPERSE P-NS manufactured by Diafloc Co., Ltd.) wasadded in an amount of 0.3% based on the weight of the fibers. Using aTAPPI standard sheet machine, a polyester fiber layer having a basisweight of 6 g/m² was formed as the first layer, a Manila hemp fiberintermediate layer having a basis weight of 3, 5, 8, 10 or 15 g/m² wasformed as the second layer, and a polyester fiber layer having a basisweight of 6 g/m² was formed as the third layer. These layers wereunified by paper making such that the wet second layer was superimposedon the surface of the wet first layer picked up on a filter paper, onwhich the wet third layer was superimposed by picking up. The resultingcombined sheet was pressed for dewatering and dried on a cylindricaldrier for experimental use at 110° C. to obtain a 3-layer paper havingthe Manila hemp fiber intermediate layer interposed between twopolyester fiber layers. The intralayer peel strength was measured bydelamination in the intermediate layer. The peel resistance of theintermediate layer composed of the Manila hemp fibers having an averagefiber length of 4.3 mm was found to be lowered as the basis weightincreased. In this case, the peel strength of the intermediate layer wasgreater than 10 N/m even when the basis weight was 15 g/m². Thus, thedelamination was not able to be carried out in a stable manner andvariation of the thickness of the delaminated sheets was large. On theother hand, the peel resistance of the intermediate layer composed ofthe Manila hemp fibers having an average fiber length of 1.3 mm wasfound to be 20 N/m when the basis weight was 3 g/m². However, the peelresistance decreased to 9.6 N/m, 6.5 N/m, 5.5 N/m and 5 N/m, when thebasis weight increased to 5 g/m², 8 g/m², 10 g/m² and 15 g/m²,respectively. Thus, delamination was able to be performed in a stablemanner when the basis weight was in the range of 5 g/m² to 10 g/m².Similar peel resistance was also obtained, when the basis weight wasabove 10 g/m². When the basis weight was 15 g/m², however, variation inthe thickness of the tissue sheets obtained by the delamination wasdisadvantageously large.

(II) Preparation of Multi-Layer Paper Having Intermediate LayerIncluding Polyester Fibers (1):

A slurry containing 90 mass % of stretched polyester fibers (TM04PNmanufactured by Teijin Ltd.) having a fineness of 0.1 dtex and a lengthof 3 mm were mixed with 10 mass % of non-stretched polyester fibers(TK08PN manufactured by Teijin Ltd.) having a fineness of 0.2 dtex and alength of 3 mm to prepare a stock for forming an intermediate layer.Using this slurry in amounts corresponding to the basis weights of 1, 2,5, 6, 8, 10 and 15 g/m², 3-layer papers were prepared in the same manneras that described (I) immediately above. The thus obtained 3-layerpapers were measured for the peel resistance at their intermediatelayers. When the basis weight was 1 g/m², the peel strength was 20 N/mso that the intralayer delamination was not able to be performed.However, the peel resistance decreased to 10.0 N/m, 1.3 N/m, 0.6 N/m,0.5 N/m, 0.5 N/m and 0.5 N/m, when the basis weight increased to 2 g/m²,5 g/m², 6 g/m², 8 g/m², 10 g/m ² and 15 g/m², respectively. Thus, thepeel resistance was nearly constant when the basis weight was 5 g/m² ormore. The delamination occurred in a stable manner along a planebisecting the intermediate layer having a basis weight of 2 g/m² to 8g/m². When the basis weight was 10 g/m² or more, however, thedelamination was not able to be performed in a stable manner so that thevariation in the thickness of the tissue sheets was large.

(III) Preparation of Multi-Layer Paper Having Intermediate LayerIncluding Polyester Fibers (2), (3):

A slurry containing 100 mass % of non-stretched polyester fibers (TK08PNmanufactured by Teijin Ltd.) having a fineness of 0.2 dtex and a lengthof 3 mm was prepared to form a stock for an intermediate layer. Usingthis slurry in an amount corresponding to the basis weight of 6 g/m², a3-layer paper was prepared in the same manner as that described (I)above. Also prepared was a slurry containing 85 mass % of stretchedpolyester fibers (TM04PN manufactured by Teijin Ltd.) having a finenessof 0.1 dtex and a length of 3 mm and 15 mass % of polyester binderfibers (sheath component: low melting point PET, fusing temperature:110° C.; core component: PET; MELTY 4080 manufactured by Unitika Ltd.)having a fineness of 1.7 dtex and a length of 5 mm. Using this slurry inan amount corresponding to the basis weight of 6 g/m², a 3-layer paperwas prepared in the same manner as that described (I) above.

The thus obtained two sheets of 3-layer papers were measured for thepeel resistance at their intermediate layers. When the intermediatelayer was composed of the 100 mass % non-stretched polyester fibers, thepeel strength was 7.5 N/m so that the intralayer delamination wasperformed in a stable manner. When the intermediate layer containedbinder fibers, however, the 3-layer paper was tightly integrated so thatdelamination was not able to be performed.

From the above results, the suitable range of the basis weight ofMulti-layer Paper B having an intralayer-peelable intermediate layer is2-8 g/m², preferably 2-6 g/m², more preferably 2-4 g/m², when theintermediate layer is composed mainly of polyester fibers, and 5-10g/m², preferably 5-8 g/m², more preferably 5-6 g/m², when theintermediate layer is composed mainly of cellulose fibers.

According to the present invention, tissue sheets having a low basisweight may be obtained by using the above-described Multi-layer Paper Aand Multi-layer Paper B. In this case, the term “tissue sheet” isintended to refer to a tissue paper obtained from Multi-layer Paper A orMulti-layer Paper B by delamination. The tissue sheet obtainable fromMulti-layer Paper A is a single-layer-sheet or a multi-layer sheet. Thetissue sheet obtainable from Multi-layer Paper B is composed of asingle-layer sheet and a nearly halved intermediate layer or of amulti-layer sheet and a nearly halved intermediate layer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic illustration of a multi-layer paper according tothe present invention which is being delaminated with a delaminationdevice;

FIG. 2(a) is a sectional view schematically illustrating a polymerfilm-Multi-layer Paper A laminate formed by bonding a polymer film toeach of the both sides of Multi-layer Paper A;

FIG. 2(b) is a schematic illustration of the laminate of FIG. 2(a) beingdelaminated-at the peelable interface;

FIG. 3(a) is a sectional view schematically illustrating a polymerfilm-Multi-layer Paper B laminate formed by bonding a polymer film toeach of the both sides of Multi-layer Paper B; and

FIG. 3(b) is a schematic illustration of the laminate of FIG. 3(a) beingdelaminated at the intralayer peelable intermediate layer.

A method of preparing tissue sheets by using Multi-layer Paper A andMulti-layer Paper B according to the present invention will be nextdescribed with reference to FIG. 1.

FIG. 1 schematically illustrates a delamination device. In FIG. 1, thereference numberals 1 and 2 denote rollers, 3 and 4 denote backingrolls, 5 a multi-layer paper, 8 a peeling section and 9 and 10 denotetissue sheets. A peelable multi-layer paper 7 supplied from a feed partis passed through a uniform low pressure nip 5 (not shown) formedbetween at least two parallel horizontal rolls 1 and 2 and isdelaminated at a peelable portion of the multi-layer paper into the twotissue sheets 9 and 10 when discharged from a substantially outlet ofthe nip. The thus obtained tissue sheets 9 and 10 are displaced at aspeed equal to the speed of the roll with their whole widths beingmaintained in contact with respective rolls, and wound around respectivetake-up rolls 6, 6′ (not shown).

The two, upper and lower horizontal rolls preferably have associatedbacking rolls 3 and 4 for preventing departure of tissue sheets fromroll surfaces during transportation and for stabilizing the position ofthe peeling section. In this case, the tension applied to the tissuesheets 9 and 10 is greater than 10 N/m and is controlled below theelastic limit of their tensile strengths. It is preferred that thetissue sheets thus obtained by delamination be subjected to a heatcalendar treatment for removing fuzz of the surfaces thereof and fallingoff of the fibers from the surfaces thereof. In this case, the thermalcalendar treatment is preferably carried out before the two tissuesheets 9 and 10 have been wound around the take-up rolls 6 and 6′. Inplace of the thermal calendaring treatment, a resin coating methodusing, for example, an urethane resin may be adopted for removingfuzzing of the surfaces thereof and falling off of the fibers from thesurfaces thereof. When the tissue sheets are obtained by intralayerdelamination of the intermediate layer having a peel strength of 10 N/mor less, fuzz of the peeled surfaces and falling off of fibers therefromoccur significantly. In such a case, the resin coating method using, forexample, an urethane resin is effective.

According to the present invention, there is provided a reinforcedmulti-layer paper material having a reinforcing member bonded to one orboth sides of the above-described Multi-layer Paper A or Multi-layerPaper B. By using the reinforcing member, it is possible to preparereinforcing member-bonded tissue sheets with high productivity at lowcosts in a stable manner.

From the above reinforcing member-multi-layer paper laminate, a tissuesheet reinforced by the reinforcing member may be prepared by simplydelaminating the reinforcing member-multi-layer paper laminate toseparate the tissue sheet reinforced by the reinforcing member using thedelamination device shown in FIG. 1.

Namely, by using the above reinforcing member-multi-layer paper laminatehaving the reinforcing member provided on one side of the multi-layerpaper in lieu of the multi-layer paper 7 in FIG. 1, reinforcingmember-multi-layer paper laminate 9 may be obtained. By using thelaminate having the reinforcing member provided on each side of themulti-layer paper, reinforcing two, member-multi-layer paper laminates 9and 10 may be obtained.

Any conventionally employed reinforcing member, such as a polymer filmor a metal foil (e.g. aluminum foil or copper foil), may be used. Thepolymer film may be, for example, a thermoplastic resin film or athermosetting resin film and has a thickness of generally 1-100 μm,though the thickness varies with the intended use. The polymer film maybe a non-porous film or a porous film.

According to the present invention, a high quality product of aheat-sensitive stencil printing master of a type in which athermoplastic polymer (resin) film is bonded on a porous support may beobtained, when the above-described tissue sheet is used as the poroussupport.

The tissue sheet used as a porous support of a heat-sensitive stencilprinting master may be a single-layer sheet or a multi-layer tissuesheet and has a basis weight of 1-20 g/m², preferably 1-10 g/m².

According to the present invention, a substrate having a low basisweight may be prepared with high productivity and at low costs by usingthe above multi-layer paper as a porous support material for producing aheat-sensitive stencil printing master.

According to the present invention, a heat-sensitive stencil printingmaster having a low basis weight may be prepared with high productivityand at low costs by using a laminate obtained by bonding a thermoplasticpolymer film to at least one side of the multi-layer paper.

According to the present invention, a high quality, heat-sensitivestencil printing master comprising a porous support, and a thermoplasticpolymer film bonded to the porous support may be prepared with highproductivity and at low costs by using the above-described tissue paperas the support.

According to the present invention, a heat-sensitive stencil printingmaster may be prepared with high productivity and at low costs by a stepof separating a tissue sheet from the above-described porous supportmaterial, and a step of bonding a thermoplastic polymer film to thepeeled surface of the separated tissue sheet.

According to the present invention, a heat-sensitive stencil printingmaster may be prepared with high productivity and at low costs byseparating, from the above-described material for producing aheat-sensitive stencil printing master, a laminate having the thin sheetto which the thermoplastic polymer film has been bonded.

The thermoplastic polymer film may be bonded to Multi-layer Paper A or Bby any conventional method such as a bonding method using an adhesive ora bonding method using melt adhesion.

Any known thermoplastic resin film conventionally used for use in theheat-sensitive stencil printing master according to the presentinvention, such as polyester, polyamide, polypropylene, polyethylene,polyvinyl chloride or polyvinylidene chloride may be used for thepurpose of the present invention. For reasons of perforationsensitivity, a polyester film is especially preferably used.

As preferred polyesters for the polyester film, there may be mentionedpolyethylene terephthalate, copolymers of ethylene terephthalate withethylene isophthalate and copolymers of hexamethylene terephthalate withcyclohexanedimethylene terephthalate. Especially preferably used forreasons of improved perforation sensitivity are copolymers of ethyleneterephthalate with ethylene isophthalate and copolymers of hexamethyleneterephthalate with cyclohexanedimethylene terephthalate.

The thermoplastic resin film may contain a flame retardant, a heatstabilizer, an oxidation preventing agent, a UV absorbing agent, anantistatic agent, a pigment, a dye an organic lubricant (e.g. a fattyacid ester or wax) and an antifoaming agent (e.g. polysiloxane), ifnecessary. A slippage may be imparted to the thermoplastic resin film.As a method for imparting the slippage, there may be mentioned a methodin which inorganic particles such as clay, mica, titanium oxide, calciumcarbonate, kaolin, talc and silica or organic particles such aspolyacrylic acid and polystyrene are incorporated or a method in which asurfactant is applied to a surface of the film.

The thickness of the thermoplastic resin film is generally preferably0.1-5.0 μm, more preferably 0.1-3.0 μm. When the thickness exceeds 5.0μm, the perforation characteristics may become sometimes poor. Too smalla thickness below 0.1 μm may sometimes adversely affect stability in thefilm forming properties and printing resistance.

For bonding the thermoplastic resin film to the tissue sheet, a methodusing an adhesive is preferable. As the adhesive, there may be mentioneda vinyl acetate-based adhesive, an acrylic adhesive, a polyester-basedadhesive, an urethane-based adhesive, an epoxy-based adhesive, anEVA-based adhesive and an ionizing radiation-type adhesive.

The amount of the adhesive applied is suitably 0.1 g/m² to 3.0 g/m²,preferably 0.2 g/m² to 1.5 g/m² on the dry basis.

When the delamination for the preparation of a heat-sensitive stencilprinting master using a laminate of a polymer film and a multi-layerpaper is carried out in the unified intereface of the multi-layer sheetafter the thermoplastic resin film has been bonded to the multi-layerpaper and when the adhesive layer penetrates into the paper layerinterface of the multi-layer paper, there is a possibility that thedelamination cannot easily occur. Therefore, the coating must be carriedout using an adhesive whose viscosity is such that the adhesive does notpenetrates into the paper layer interface of the multi-layer paper. Inthe case where the intralayer delamination is conducted in theintermediate layer, too, the coating must be carried out using anadhesive whose viscosity is such that the adhesive does not penetratesinto the intermediate paper layer of the multi-layer paper. Theviscosity of the adhesive is thus to be suitably selected and controlledby dilution with a solvent or by heating. The controlling method is notspecifically limited, however.

The adhesive may be incorporated with an antistatic agent, if desired.Illustrative of suitable antistatic agents are cation, anion, noion,amphoteric; carbon; and electrically conducting materials.

It is preferred that a thin layer containing ingredients such as asilicone oil, a silicone resin, a fluorine-containing resin, asurfactant, an antistatic agent, a heat resisting agent, an oxidationpreventing agent, organic particles, inorganic particles, a pigment, adispersion aid, an antiseptic agent and a antifoaming agent, be formedon that surface of the heat-sensitive stencil printing master which isto be contacted with a thermal head for the purpose of preventingmelt-adhesion during perforation. The melt-adhesion preventing thinlayer preferably has a thickness of 0.005-0.4 μm, more preferably0.01-0.4 μm.

A method of forming a thin layer for the prevention of melt-adhesion ofa heat-sensitive stencil printing master of the present invention is notspecifically limited. One preferred method includes applying a solutionof the adhesive diluted with water or a solvent with a coater such as aroll coater, a gravure coater, reverse coater or bar coater, followed bydrying.

Next, a method of preparing a heat-sensitive stencil printing masterusing a laminate of a polymer film and a multi-layer paper as a materialfor the preparing the heat-sensitive stencil printing master will bedescribed in detail with reference to the drawings.

FIG. 2(a) depicts a laminate of a polymer film and Multi-layer Paper Aobtained by a method including combining two wet embryonic layers bypaper making, drying the combined sheet to obtain a multi-layer paper(2-layer paper) A(I) composed of a paper layer 1A and a paper layer 1B,laminating a polymer film 2A on one side thereof, and laminating apolymer film 2B on the other side thereof.

For the preparation of heat-sensitive stencil printing masters from thethus obtained laminate, the multi-layer paper A(I) is delaminated, asshown in FIG. 2(b), at the peelable interface between the paper layer 1Aand the paper layer 1B, thereby obtaining a master paper 3A having thepolymer film 2A formed on the paper layer 1A and a master paper 3Bhaving the polymer film 2B formed on the paper layer 1B.

FIG. 3(a) depicts a laminate of a polymer film and Multi-layer Paper Bobtained by a method including combining three wet embryonic layers bypaper making, drying the combined sheet to obtain a multi-layer paper(3-layer paper) B(I) composed of a paper layer 1C, a paper layer 1E anda paper layer 1D, laminating a polymer film 2C on one side thereof, andlaminating a polymer film 2D on the other side thereof.

For the preparation of heat-sensitive stencil printing masters from thethus obtained laminate, the multi-layer paper B(I) is delaminated, asshown in FIG. 3(b), at the intralayer peelable paper layer 1E, therebyobtaining a master paper 3E having the polymer film 2C formed on thepaper layer 1C and a master paper 3F having the polymer film 2D formedon the paper layer 1D.

EXAMPLES

The present invention will be described by examples but is not limitedthereto. Peel strength in Examples and Comparative Examples is evaluatedaccording to the following method.

Peel Strength Evaluating Method:

A sample sheet used for evaluating the peel strength in the interface atwhich two layers are combined by paper making and in an intermediatelayer of a multi-layer paper has a size of 15 mm×150 mm with thelengthwise direction of the sample coinciding with the machinedirection. An edge portion (about 20 mm) of one end of the sample ismanually peeled at an interface or internally within an intermediatelayer and the peeled portions are folded outward so that the sample isshaped into a T-like form. Folded portions are held by grips of aconstant speed-type tensile tester (Tensilon manufactured by ToyoMeasuring Instrument Co., Ltd.) which grips are spaced apart a distanceof 25 mm from each other. The grips are then displaced in oppositedirections at a displacing rate of 300 mm/minute while recording thepeel strength by the tester. During the displacement of the grips, thenon-peeled portion of the sample is supported by fingers and maintainedin a T-shaped form. The load (N) for peeling at a point in time whereabout 50 mm portion of the sample has been peeled from the start of thedisplacement of the grips is determined by optimum linear method. Thepeel strength (N/m) is obtained by dividing such a load by the width ofthe sample. The moisture control and measurement for the sample wascarried out in a thermostatic chamber at a temperature of 23° C. and arelative humidity of 50%.

Example 1 and Comparative Example 1

A Manila hemp pulp was beaten to obtain a stock having Canadian Standardfreeness (CSF) 680. A layer of the furnish formed on a wire of a TAPPIstandard sheet machine was picked up on a filter paper in an amountcorresponding to a basis weight of 10 g/m². Similar two layers wereformed on separate filter papers. One of the wet layers was smoothedwith a roll and was then combined with the other layer such that thesmoothed surface was in contact with the other layer. The combined sheetwas pressed for dewatering and dried on a cylindrical drier for anexperiment use at 110° C. to obtain a two-layer paper. For the purposeof comparison, the above procedures were repeated in the same manner asdescribed except that the smoothing treatment was not carried out,thereby obtaining a two-layer paper of Comparative Example 1. The peelstrength of each of the above two-layer papers was measured. Thetwo-layer paper of Example 1 which was subjected to a smoothingtreatment was found to have a peel strength of 9.8 N/m. The two-layerpaper was able to be separated uniformly at the interface therebetween.The peel strength of the two-layer paper of Comparative Example 1 wasfound to be 14 N/m. The paper was not able to be smoothly separated andcaused partial breakage of the paper layers.

Example 2

60 Mass % of non-stretched polyester fibers (TEPYRUS TKO8PN manufacturedby Teijin Ltd.) having a fineness of 0.2 dtex and a length of 3 mm weremixed with 40 mass % of polyester binder fibers (sheath component: lowmelting point PET, fusing temperature: 110° C.; core component: PET;SOFIT N720 manufactured by Kuraray Co., Ltd.) having a fineness of 1.7dtex and a length of 5 mm, to which an acrylamide-type dispersing agent(ACRYPERSE P-NS manufactured by Diafoc Co., Ltd.) was added in an amountof 0.3 mass % (based on total fibers) to obtain a stock for a firstlayer. The first layer of polyester fibers was formed on a wire of aTAPPI standard sheet machine in an amount corresponding to a basisweight of 5 g/m². A Manila hemp pulp was beaten to Canadian Standardfreeness (CSF) 550 to obtain a stock for a second layer. The secondlayer of the Manila hemp fibers was formed on a wire of a TAPPI standardsheet machine in an amount corresponding to a basis weight of 8 g/m².Next, using the same stock as that of the first layer, a third layer ofpolyester fibers was formed on a wire of a TAPPI standard sheet machinein an amount corresponding to a basis weight of 5 g/m². These paperlayers were then successively superimposed one over the other forunification by paper making. The unification by the paper making wascarried out in the following manner. Thus, the first layer of the wetpaper on the filter paper was overlaid with the second layer of the wetpaper by picking up. The surface of the second layer was then overlaidwith the third layer of the wet paper by picking up. The resultingcombined wet sheet was pressed for dewatering and dried on a cylindricaldrier at 105° C. for use in experiments, thereby to obtain a unified3-layer paper according to the present invention having two polyesterfiber layers between which the hemp fiber layer was interposed. The peelstrength of the 3-layer paper was found to be 1.97 N/m between the firstlayer and the second layer and 2.11 N/m between the second layer and thethird layer. By the peeling, three tissue sheets composed of two tissuesheets made of polyester fibers and one tissue sheet made of Manila hempfibers were obtained. The physical properties of the three-layer paperand tissue sheets are shown in Table 1. Fuzz of the peeled surfaces andliberation of fibers from the layers were tolerable.

Preparation of Heat-Sensitive Stencil Printing Master:

A 5 mass % toluene solution of a polyester resin (ELEETEL 3500manufactured by Unitika Ltd.) was applied in an amount of 0.5 g/m² (ondry basis) on one surface of a biaxially oriented polyester film havinga thickness of 2.0 μm. The 3-layer paper obtained above was superimposedon the non-dried coating on the polyester film such that the firstpolyester fiber layer was contacted with the polyester coating. This wasthen dried with a dryer to obtain a laminate (material for preparing aheat-sensitive stencil printing master). The 3-layer paper of thelaminate was peeled at the interface between the first and second layersto leave a laminate composed of the first layer and the film. A 1.0 mass% toluene solution of a silicone oil (SF8422 manufactured by ShinetsuKagaku Co., Ltd.) was applied using a smooth bar to the other surface ofthe polyester film of the laminate and dried to form a melt-adhesionpreventing layer thereon, thereby obtaining a heat-sensitive stencilprinting master.

A second heat-sensitive stencil printing master which was a compositecomposed of a tissue paper of the second layer and a film was preparedin the same manner as described above except that the second layer fromthe remaining laminate composed of the second and third layers wassuperimposed on and bonded to a polyester film. Further, a thirdcomposite composed of a tissue paper of the third layer and a film wasprepared in the same manner as described above except that the thirdlayer was superimposed on and bonded to a polyester film such that thepeeled surface of the third layer was in contact with the film.

Using the thus obtained three kinds of the heat-sensitive stencilprinting masters, plating and printing were performed with a printer(VT2820 manufactured by Ricoh Company, Ltd.). The tissue papers of thepolyester fibers layer were found to be usable as a porous support forso-called high grade images free of white spots. The tissue paper of theManila hemp fiber layer was found to be usable for printing as a poroussupport for so-called low grade images though white spots were formed.

Example 3

Example 2 was repeated in the same manner as described except that thebasis weight of the polyester fiber layers was reduced to 1 g/m² toobtain a unified 3-layer paper. A biaxially oriented polyester filmhaving a thickness of 2.0 μm was bonded with an adhesive to each of theopposing surfaces of the 3-layer paper to obtain a laminate sheet(reinforced multi-layer paper material). The laminate sheet was found tobe delaminatable at the interface between the first and second layers.The physical properties of the three-layer paper were as shown in Table1.

Preparation of Heat-Sensitive Stencil Printing Master:

A 10 mass % ethyl acetate solution of a damp-setting type polyurethaneresin (TAKENATE manufactured by Takeda Chemical Industries Ltd.) wasapplied in an amount of 0.4 g/m² (on dry basis) on one surface of abiaxially oriented polyester film having a thickness of 2.0 μm and driedwith a dryer. This was then superimposed on the 3-layer paper obtainedabove such that the dried coating was contacted with the outer surfaceof the first layer of the 3-layer paper. The assembly was overlaid witha weight and allowed to stand at 40° C. for 2 days to perform curing.The 3-layer paper was peeled at the interface between the first layerand the second to leave a polyester-tissue paper laminate. A 1.0 mass %toluene solution of a silicone oil (SF8422 manufactured by ShinetsuKagaku Co., Ltd.) was applied using a smooth bar to the other surface ofthe polyester film and dried to form a melt-adhesion preventing layerthereon, thereby obtaining a heat-sensitive stencil printing master.Using the thus obtained stencil printing master was perforated andprinting was performed with a printer (Priport VT2820 manufactured byRicoh Company, Ltd.). The stencil paper was found to have good inkpermeability and to give prints without white spots.

Example 4

Example 2 was repeated in the same manner as described except that eachof the polyester fiber layers was composed of 80 mass % of non-stretchedpolyester fibers (TKO8PN manufactured by Teijin Ltd.) having a finenessof 0.2 dtex and a length of 3 mm and 20 mass % of polyester binderfibers (sheath component: low melting point PET, fusing temperature:110° C.; core component: PET; SOFIT N720 manufactured by Kuraray Co.,Ltd.) having a fineness of 1.7 dtex and a length of 5 mm to obtain a3-layer paper. The peel strength of the 3-layer paper was found to be1.76 N/m between the first polyester fiber layer and the Manila hemplayer and 1.79 N/m between the second polyester fiber layer and theManila hemp layer. The 3-layer paper was able to be uniformly separatedinto three tissue sheets, namely two polyester fiber tissue sheets andone Manila hemp sheet. The physical properties of the 3-layer paper andthe tissue sheets are shown in Table 1. Fuzz of the peeled surfaces andliberation of fibers from the layers were more noticeable but wastolerable.

Example 5

Example 2 was repeated in the same manner as described except that eachof the first and third polyester fiber layers was composed of 100 mass %polyester binder fibers (sheath component: low melting point PET, fusingtemperature: 110° C.; core component: PET; SOFIT N720 manufactured byKuraray Co., Ltd.) having a fineness of 1.7 dtex and a length of 5 mm toobtain a 3-layer paper. The peel strength of the 3-layer paper was foundto be 2.26 N/m between the first polyester fiber layer and the hemplayer and 2.31 N/m between the second polyester fiber layer and the hemplayer. The 3-layer paper was able to be uniformly separated into threetissue sheets, namely two polyester fiber tissue sheets and one Manilahemp sheet. The physical properties of the 3-layer paper and the tissuesheets are shown in Table 1. Fuzz of the peeled surfaces and liberationof fibers from the layers were least noticeable. These tissue sheetswere suitable as a porous support for heat-sensitive stencil printingmaster.

Preparation of Heat-Sensitive Stencil Printing Master:

Using the thus obtained three kinds of tissue sheets, threeheat-sensitive stencil printing masters were prepared in the same manneras that in Example 2. Preparation of printing plates and printing usingsame were performed with a printer (Priport VT2820 manufactured by RicohCompany, Ltd.). The tissue sheets of the polyester fiber layers werefound to be usable as high grade porous supports without white spots.The tissue sheet of the Manila hemp fibers was found to be usable as aporous support for low grade images which gives suitable prints althoughwhite spots are formed.

Example 6

Example 2 was repeated in the same manner as described except that amixture composed of 90 Parts by weight of Manila hemp pulp beaten toCanadian Standard freeness (CSF) 550 and 10 parts by weight of polyesterbinder fibers (sheath component: low melting point PET, fusingtemperature: 110° C.; core component: PET; SOFIT N720 manufactured byKuraray Co., Ltd.) having a fineness of 1.7 dtex and a length of 5 mmwas used as the stock for the second layer to obtain a 3-layer paper.The peel strength of the 3-layer paper was found to be 5.49 N/m betweenthe first polyester fiber layer and the hemp layer and 5.33 N/m betweenthe second polyester fiber layer and the hemp layer, although peelstrengths were slightly greater. The 3-layer paper was able to beuniformly separated into three tissue sheets, namely two polyester fibertissue sheets and one tissue sheet composed of Manila hemp fibers mixedwith the polyester binder fibers. The physical properties of the 3-layerpaper and the tissue sheets are shown in Table 1. Fuzz of the peeledsurfaces and liberation of fibers from the layers were most noticeable.The fuzz of the surface fibers and liberation of fibers no longeroccurred when the tissue sheets were subjected to a hot calendaringtreatment.

Comparative Example 2

Example 2 was repeated in the same manner as described except that themixing ratio of the polyester binder fibers of the stock for the secondlayer was increased by 5 mass % to 15 mass %, thereby obtaining a3-layer paper. The peel strength of the multi-layer paper was found tobe 11.84 N/m between the first layer and the second layer and 11.99 N/mbetween the second layer and the third layer, namely in excess of thepeel resistance limitation of 10 N/m. It was not possible to uniformlyseparate the multi-layer paper at each interface.

TABLE 1 Example 2 3 4 5 6 Comp. 2 Synthetic PET binder fiber 1.7 dtex ×5 mm 40% 40% 20% 100% 40% 40% fiber layer Non-stretched PET fiber 60%60% 80% — 60% 60% 0.2 dtex × 3 mm Basis weight (g/m²) 5.0 1.0 5.0 5.05.0 5.0 Cellulose Manila hemp pulp 100% 100% 100% 100% 90% 85% fiberlayer PET binder fiber 1.7 dtex × 5 mm — — — — 10% 15% Basis weight(g/m²) 8.0 8.0 8.0 8.0 8.0 8.0 Synthetic PET binder fiber 1.7 dtex × 5mm 40% 40% 20% 100% 40% 40% fiber layer Non-stretched PET fiber 60% 60%80% — 60% 60% 0.2 dtex × 3 mm Basis weight (g/m²) 5.0 1.0 5.0 5.0 5.05.0 Drying ° C. 105 105 105 105 105 105 Temperature Multi-layer Basisweight (g/m²) 18.88 10.13 18.40 17.62 18.42 18.36 paper Density (g/cm³)0.321 0.290 0.333 0.259 0.318 0.312 Tensile strength (kN/m) 0.66 0.410.71 0.61 0.67 0.67 Synthetic Basis weight (g/m²) 5.37 — 5.46 5.26 5.43— fiber tissue Density (g/cm³) 0.190 — 0.226 0.159 0.200 — sheet Tensilestrength (kN/m) 0.134 — 0.102 0.160 0.130 — Peel strength (N/m) 1.97 —1.76 2.26 5.49 11.84 Cellulose Basis weight (g/m²) 8.19 — 7.85 7.57 7.95— fiber tissue Density (g/cm³) 0.273 — 0.278 0.277 0.272 — sheet Tensilestrength (kN/m) 0.255 — 0.240 0.238 0.265 — Peel strength (N/m) 2.11 —1.79 2.31 5.33 11.99 Synthetic Basis weight (g/m²) 5.32 — 5.09 4.79 5.04— fiber tissue Density (g/cm³) 0.190 — 0.224 0.158 0.198 — sheet Tensilestrength (kN/m) 0.134 — 0.099 0.155 0.126 —

Example 7

60 Mass % of non-stretched polyester fibers (TEPYRUS TKO8PN manufacturedby Teijin Ltd.) having a fineness of 0.2 dtex and a length of 3 mm weremixed with 40 mass % of polyester binder fibers (sheath component: lowmelting point PET, fusing temperature: 110° C.; core component: PET;MELTY 4080 manufactured by Unitika Ltd.) having a fineness of 1.5 dtexand a length of 5 mm, to which an acrylamide-type dispersing agent(ACRYPERSE P-NS manufactured by Diafloc Co., Ltd.) was added in anamount of 0.3% to obtain a stock for forming first and third layers. AManila hemp pulp was beaten to Canadian Standard freeness (CSF) 700 toobtain a stock for a second layer.

Using a paper machine having a first cylinder wire section, a short wiresection and a second cylinder wire section, a 3-layer paper of polyesterfiber layer-Manila hemp fiber layer-polyester fiber layer according tothe present invention was manufactured by unification by paper making.Thus, the polyester fiber layer stock was fed to the first cylinder wiresection in an amount providing a target basis weight of 2 g/m² and tothe second cylinder wire section in an amount providing a target basisweight of 5.0 g/m² while the Manila hemp fiber layer stock was fed tothe short wire section in an amount providing a target basis weight of6.5 g/m².

The peel strength of the 3-layer paper was found to be 1.97 N/m betweenthe third, polyester fiber layer and the second, hemp fiber layer. Theselayers were delaminated uniformly at the interface therebetween. Fuzz ofthe surface and liberation of fibers from the layers of the thusobtained tissue sheets were found to be much less noticeable as comparedwith those obtained by hand paper machine. When measured with StiffnessTester manufactured by L & W Inc. in the machine direction (MD) with asample width of 38 mm, a bending length of 1 mm and a bending angle of25°, a tissue sheet of the third, polyester fiber layer and a tissuesheet of the remaining composite sheet composed of the first, polyesterfiber layer and the Manila hemp fiber layer had flexural rigidity of 5.5mN and 26 mN, respectively. A heat-sensitive stencil printing master wasprepared using the 2-layer tissue sheet as a porous support in such amanner that a thermoplastic resin film was applied to the polyesterfiber layer. The porous support had good ink permeability and stiffness.The 3-layer paper and two tissue sheets obtained therefrom hadproperties summarized in Table 2.

Preparation of Heat-Sensitive Stencil Printing Master:

A 5 mass % toluene solution of a polyester resin (ELEETEL manufacturedby Unitika Ltd.) was applied with a gravure coater in an amount of 0.5g/m² (on dry basis) on one surface of a biaxially oriented polyesterfilm having a thickness of 2.0 μm. On the non-dried coating on thepolyester film, the 3-layer sheet prepared above was superimposed suchthat the outer surface of the first layer was contacted with thepolyester coating to obtain a laminate sheet. The laminate sheet waspeeled at the interface between the second layer and the third layer toobtain a polyester film-tissue paper laminate. A 1.0 mass % toluenesolution of a silicone oil (SF8422 manufactured by Shinetsu Kagaku Co.,Ltd.) was applied using a smooth bar to the other surface of thepolyester film and dried to form a melt-adhesion preventing layerthereon, thereby obtaining a heat-sensitive stencil printing master. Thethus obtained stencil printing master was perforated and printing wasperformed with a printer (Priport VT2820 manufactured by Ricoh Company,Ltd.). Good results were obtained.

Example 8

60 Mass % of non-stretched polyester fibers (TEPYRUS TKO8PN manufacturedby Teijin Ltd.) having a fineness of 0.2 dtex and a length of 3 mm weremixed with 40 parts by weight of polyester binder fibers (sheathcomponent: low melting point PET, fusing temperature: 110° C.; corecomponent: PET; SOFIT N720 manufactured by Kuraray Co., Ltd.) having afineness of 1.7 dtex and a length of 5 mm, to which an acrylamide-typedispersing agent (ACRYPERSE P-NS manufactured by Diafloc Co., Ltd.) wasadded in an amount of 0.3% to obtain a stock for a polyester fiberlayer. A Manila hemp pulp was beaten to Canadian Standard freeness (CSF)716 and mixed with 0.75 mass % (based on the fibers) of a polyethylenewax (PERTOL N856 manufactured by Kindai Chemical Industry Co., Ltd.) toobtain a stock for a Manila hemp fiber layer.

Using a paper machine having a cylinder wire section and a short wiresection, a 2-layer paper according to the present invention wasmanufactured. Thus, the polyester fiber layer stock was fed to the shortwire section in an amount providing a target basis weight of 5 g/m²,while the Manila hemp fiber layer stock was fed to the cylinder wiresection in an amount providing a target basis weight of 7.5 g/m² forunification of the two layers by paper making. In this case, the wetManila hemp fiber layer was smoothed with a mesh wire roll prior to theunification. The peel strength of the 2-layer paper at the interface wasfound to be 1.7 N/m. The sheet was able to be easily and uniformlyseparated into a tissue sheet of the polyester fibers and a tissue sheetof the Manila hemp fibers. The 2-layer paper and the two tissue sheetshad the properties summarized in Table 2. The tissue sheet of thepolyester fiber was found to be suitable for use as a porous support fora heat-sensitive stencil printing master.

Example 9

40 Mass % of non-stretched polyester fibers (TEPYRUS TKO8PN manufacturedby Teijin Ltd.) having a fineness of 0.2 dtex and a length of 3 mm weremixed with 20 mass % of non-stretched polyester fibers (EP101manufactured by Kuraray Co., Ltd.) having a fineness of 1.1 dtex and alength of 3 mm and with 40 mass % of polyester binder fibers (sheathcomponent: low melting point PET, fusion temperature: 110° C.; corecomponent: PET; MELTY 4080 manufactured by Unitika Ltd.) having afineness of 1.1 dtex and a length of 3 mm, to which an acrylamide-typedispersing agent (ACRYPERSE P-NS manufactured by Diafloc Co., Ltd.) wasadded in an amount of 0.3% based on the weight of the fibers to obtain astock for a polyester fiber layer. A Manila hemp pulp was beaten toCanadian Standard freeness (CSF) 594 and mixed with 0.75 mass % (basedon the fibers) of a polyethylene wax (PERTOL N856 manufactured by KindaiChemical Industry Co., Ltd.) as a releasing agent to obtain a stock fora Manila hemp fiber layer.

Using a paper machine having a first cylinder wire section, a short wiresection and a second cylinder wire section, a 3-layer paper according tothe present invention was manufactured by unification by paper making.Thus, the polyester fiber layer stock was fed to the first and secondcylinder wire sections each in an amount providing a target basis weightof 5 g/m², while the Manila hemp fiber layer stock was fed to the shortwire section in an amount providing a target basis weight of 8 g/m². Thepolyester fiber wet layer picked up on a felt from the first cylindersection was smoothed with a mesh wire roll before unification by papermaking. The peel strength of the 3-layer paper was 2.1 N/m at theinterface between the layer produced in the first cylinder wire sectionand the layer produced in the short wire section and 2.3 N/m at theinterface between the layer produced in the short wire section and thelayer produced in the second cylinder wire section. The 3-layer papercould be uniformly delaminated. The 3-layer paper was subjected todelamination using a device as shown in FIG. 1 to form two rolls ofpolyester fiber tissue sheets and one roll of the hemp fiber tissuesheet. The 3-layer paper and the three tissue sheets had the propertiessummarized in Table 2. Each of these tissue sheets was found to besuitable for use as a porous support for a heat-sensitive stencilprinting master.

Preparation of Heat-Sensitive Stencil Printing Masters:

A 5 mass % toluene solution of a polyester resin (ELEETEL manufacturedby Unitika Ltd.) was applied in an amount of 0.5 g/m² (on dry basis)with a gravure coater on one surface of a biaxially oriented polyesterfilm having a thickness of 2.0 μm. Each of the rolled tissue sheetsobtained above was superimposed on the non-dried coating on thepolyester film and the assembly was then dried with a dryer to obtainpolyester-tissue sheet laminates. A 1.0 mass % toluene solution of asilicone oil (SF8422 manufactured by Shinetsu Kagaku Co., Ltd.) wasapplied using a smooth bar to the other surface of the polyester filmand dried to form a melt-adhesion preventing layer thereon, therebyobtaining three kinds of heat-sensitive stencil printing masters. Thethus obtained stencil printing masters were perforated and printing wasperformed with a printer (Priport VT2820 manufactured by Ricoh Company,Ltd.). The polyester fiber tissue sheets were found to be usable as ahigh grade printing porous support which did not form white spots. Thehemp fiber tissue sheet was usable as porous support for low gradeimages which gave suitable prints though white spots were produced.

Example 10

30 Mass % of stretched polyester fibers (EP043 manufactured by KurarayCo., Ltd.) having a fineness of 0.5 dtex and a length of 5 mm were mixedwith 10 mass % of non-stretched polyester fibers (EP101 manufactured byKuraray Co., Ltd.) having a fineness of 1.1 dtex and a length of 3 mm,30 mass % of polyester binder fibers (sheath component: low meltingpoint PET, fusion temperature: 110° C.; core component: PET; MELTY 4080manufactured by Unitika Ltd.) having a fineness of 1.1 dtex and a lengthof 3 mm and 30 parts by weight of polyester binder fibers (sheathcomponent: low melting point PET, fusion temperature: 110° C.; corecomponent: PET; MELTY 4080 manufactured by Unitika Ltd.) having afineness of 1.7 dtex and a length of 5 mm, to which an acrylamide-typedispersing agent (ACRYPERSE P-NS manufactured by Diafloc Co., Ltd.) wasadded in an amount of 0.3% based on the weight of the fibers to obtain astock for a polyester fiber layer. A breached softwood kraft pulp (NBKP)was beaten to Canadian Standard freeness (CSF) 515 to obtain a stock fora wood pulp fiber layer.

Using a paper machine having a first cylinder wire section, a short wiresection and a second cylinder wire section, a 3-layer paper according tothe present invention was manufactured by unification by paper making.Thus, the polyester fiber layer stock was fed to the first and secondcylinder wire sections each in an amount providing a target basis weightof 5 g/m², while the wood pulp fiber layer stock was fed to the shortwire section in an amount providing a target basis weight of 10 g/m² inthe same manner as that in Example 8 for unification by paper making.The peel strength of the 3-layer paper was 3.6 N/m at the interfacebetween the layer produced in the first cylinder wire section and thelayer produced in the short wire section and 3.8 N/m at the interfacebetween the layer produced in the short wire section and the layerproduced in the second cylinder wire section. The 3-layer paper could beuniformly delaminated. The delamination gave two rolls of polyesterfiber tissue sheets and one roll of the wood pulp fiber tissue sheet.The 3-layer paper and the three tissue sheets had the propertiessummarized in Table 2.

Example 11

Example 9 was repeated in the same manner as described except that 0.75mass % (based on the fibers) of a polyethylene wax (PERTOL N856manufactured by Kindai Chemical Industry Co., Ltd.) as a releasing agentwas incorporated into the stock for wood pulp fiber layer to obtain a3-layer paper of the present invention. The peel strength of the 3-layerpaper was 2.7 N/m at the interface between the layer produced in thefirst cylinder wire section and the layer produced in the short wiresection and 2.8 N/m at the interface between the layer produced in theshort wire section and the layer produced in the second cylinder wiresection. The 3-layer paper could be uniformly delaminated with less peelresistance as compared with that in Example 9. The 3-layer paper and thetissue sheets had the properties summarized in Table 2.

TABLE 2 Example 7 8 9 10 11 Synthetic PET binder fiber 1.7 dtex × 5 mm40% — — 30% 30% fiber layer 1.1 dtex × 3 mm — — 40% 30% 30%Non-stretched PET fiber 0.2 dtex × 3 mm 60% — 40% — — 1.1 dtex × 3 mm —— 20% 10% 10% Stretched PET fiber 0.4 dtex × 5 mm — — — 30% 30% Amountof dispersing agent 0.3% — 0.3% 0.3% 0.3% Basis weight (g/m²) 2.0 — 5.05.0 5.0 Kind of wire *1 — *1 *1 *1 Cellulose Manila hemp pulp CSF 711716 594 — — fiber layer 100% 100% 100% — — NBKP CSF — — — 515 515 — — —100% 100% Amount of releasing agent — 0.75% 0.75% — 0.75% Basis weight(g/m²) 6.5 7.5 8.0 10.0 10.0 Kind of wire *3 *1 *3 *3 *3 Synthetic PETbinder fiber 1.7 dtex × 5 mm 40% 40% — 30% 30% fiber layer 1.1 dtex × 3mm — — 40% 30% 30% Non-stretched PET fiber 0.2 dtex × 3 mm 60% 60% 40% —— 1.1 dtex × 3 mm — — 20% 10% 10% Stretched PET fiber 0.4 dtex × 5 mm —— — 30% 30% Amount of dispersing agent 0.3% 0.3% 0.3% 0.3% 0.3% Basisweight (g/m²) 5.0 5.0 5.0 5.0 5.0 Kind of wire *2 *3 *2 *2 *2 Drying °C. 98 104 98 95 95 Temperature Example 7 8 9 10 11 Multi-layer PaperBasis weight (g/m²) 13.48 13.51 18.00 23.75 23.67 Density (g/cm³) 0.3310.313 0.339 0.324 0.319 T. strg. MD (kN/m) 0.330 0.360 1.012 0.712 0.644CD (kN/m) 0.065 0.057 0.214 0.165 0.151 Synthetic fiber tissue sheetBasis weight (g/m²) — 4.99 5.94 5.88 Density (g/cm³) — 0.200 0.198 0.196T. strg. MD (kN/m) — 0.152 0.112 0.109 CD (kN/m) 0.016 0.011 0.010 Peelstrength (N/m) — 2.3 3.6 2.7 Cellulose fiber tissue sheet Basis weight(g/m²) 8.68 8.57 8.20 12.5 12.6 Density (g/cm³) 0.294 0.283 0.328 0.3830.387 T. strg. MD (kN/m) 0.162 0.200 0.745 0.51 0.442 CD (kN/m) 0.0610.027 0.221 0.154 0.136 Peel strength (N/m) 2.0 1.7 2.1 3.8 2.8Synthetic fiber tissue sheet Basis weight (g/m²) 4.80 4.94 4.81 5.315.19 Density (g/cm³) 0.212 0.190 0.198 0.195 0.193 T. strg. MD (kN/m)0.184 0.141 0.139 0.107 0.100 CD (kN/m) 0.015 0.039 0.014 0.010 0.011*1: first cylinder wire *2: second cylinder wire *3: short wire

Example 12

A slurry containing 90 mass % of stretched polyester fibers (TM04PNmanufactured by Teijin Ltd.) having a fineness of 0.1 dtex and a lengthof 3 mm were mixed with 10 mass % of non-stretched polyester fibers(TK08PN manufactured by Teijin Ltd.) having a fineness of 0.2 dtex and alength of 3 mm was prepared as a stock for forming an intermediatelayer. As a stock for forming first and third layers to be disposedadjacent to the intermediate layer, also prepared was a slurrycontaining 40 mass % of polyester binder fibers (sheath component: lowmelting point PET, fusing temperature: 110° C.; core component: PET;MELTY 4080 manufactured by Unitika Ltd.) having a fineness of 1.7 dtexand a length of 5 mm and 60 mass % of non-stretched polyester fibers(TK08PN manufactured by Teijin Ltd.) having a fineness of 0.2 dtex and alength of 3 mm, to which an acrylamide-type dispersing agent (ACRYPERSEP-NS manufactured by Diafloc Co., Ltd.) was added in an amount of 0.3%based on the weight of the fibers.

Using a TAPPI standard sheet machine, a polyester fiber layer having abasis weight of 6 g/m² was formed as the first layer, a polyester fiberintermediate layer having a basis weight of 2 g/m² was formed as thesecond layer, and a polyester fiber layer having a basis weight of 6g/m² was formed as the third layer. These layers were unified by papermaking such that the wet second layer was superimposed on the surface ofthe wet first layer picked up on a filter paper, on which the wet thirdlayer was superimposed by picking up. The resulting combined sheet waspressed for dewatering and dried on a cylindrical drier for experimentaluse at 110° C. to obtain a 3-layer paper having three, first,intermediate and third polyester fiber layers and having an intralayerpeel strength of not greater than 10 N/m in the intermediate layer. Thepeel resistance of the intermediate layer of the 3-layer paper was foundto be 10 N/m. The intralayer delamination occurred uniformly in theintermediate layer along a plane nearly bisecting the intermediatelayer. The 3-layer paper and the tissue sheets (tissue paper) afterdelaminating had the properties summarized in Table 3.

Preparation of Heat-Sensitive Stencil Printing Masters:

A 5 mass % toluene solution of a polyester resin (ELEETEL 3500manufactured by Unitika Ltd.) was applied in an amount of 0.5 g/m² (ondry basis) on one surface of each of two, biaxially oriented polyesterfilms having a thickness of 2.0 μm. The peeled surface of each of thetissue sheets obtained above was slightly pressed with a hot surface tosuppress the fuzz and then bonded to the non-dried coating on respectivepolyester films. Each assembly was then dried with a dryer to obtainlaminates of the polyester film and the tissue sheet. A 1.0 mass %toluene solution of a silicone oil (SF8422 manufactured by ShinetsuKagaku Co., Ltd.) was applied using a smooth bar to the other surface ofeach of the polyester films and dried to form a melt-adhesion preventinglayer thereon, thereby obtaining two sheets of heat-sensitive stencilprinting masters.

Each of the heat-sensitive stencil printing masters was perforated andprinting was performed with a printer (Priport VT2820 manufactured byRicoh Company, Ltd.). Good results were obtained. The tissue sheets werefound to be usable as porous supports for high grade images withoutwhite spots.

Example 13

Example 12 was repeated in the same manner as described except that thebasis weight of the intermediate polyester fiber layers was increased to6 g/m² to obtain a 3-layer paper having an intralayer peel strength ofnot greater than 10 N/m. The peel resistance of the intermediate layerof the 3-layer paper was found to be 0.6 N/m. The intralayerdelamination occurred uniformly in the intermediate layer along a planenearly bisecting the intermediate layer. The 3-layer paper and thetissue sheets after delamination had the properties summarized in Table3.

Preparation of Heat-Sensitive Stencil:

Two sheets of heat-sensitive stencil printing masters were prepared inthe same manner as that in Example 12. Each of the heat-sensitivestencil printing masters was perforated and printing was performed witha printer (Priport VT2820 manufactured by Ricoh Company, Ltd.). Thetissue sheets were found to be usable as porous supports for high gradeimages without white spots.

Example 14

Preparation of 3-Layer Paper:

A Manila hemp pulp sheet was cut with a razor into small squares ofabout 1 mm side length and disintegrated to obtain a slurry (averagefiber length: 1.3 mm). Example 12 was repeated in the same manner asdescribed using this slurry as a stock for the intermediate layer toobtain a 3-layer paper having the intermediate layer with an intralayerpeel strength of not greater than 10 N/m. The peel resistance of theintermediate layer of the 3-layer paper was found to be 9.8 N/m. Theintralayer delamination occurred uniformly in the intermediate layeralong a plane nearly bisecting the intermediate layer.

Preparation of Heat-Sensitive Stencil Printing Masters:

A 5 mass % toluene solution of a polyester resin (ELEETEL 3500manufactured by Unitika Ltd.) was applied in an amount of 0.5 g/m² (ondry basis) on one surface of each of two, biaxially orientedpolyester-films having a thickness of 2.0 μm. The peeled surface of eachof the tissue sheets obtained above was slightly pressed with a hotsurface to suppress the fuzz and then bonded to the non-dried coating onrespective polyester films. Each assembly was then dried with a dryer toobtain laminates of the polyester film and the tissue sheet. A 1.0 mass% toluene solution of a silicone oil (SF8422 manufactured by ShinetsuKagaku Co., Ltd.) was applied using a smooth bar to the other surface ofeach of the polyester films and dried to form a melt-adhesion preventinglayer thereon, thereby obtaining two sheets of heat-sensitive printingmasters.

Each of the heat-sensitive stencil printing masters was perforated andprinting was performed with a printer (Priport VT2820 manufactured byRicoh Company, Ltd.). Good results were obtained. The tissue sheets werefound to be suited as a porous support for so-called low grade imageswhich was usable as prints though white spots existed.

TABLE 3 Example 12 13 Consti- Material PET binder fiber 40% 40% tutionfor 1st 1.7 dtex × 5 mm layer Non-stretched PET fiber 60% 60% 0.2 dtex ×3 mm Basis weight (g/m²) 6.0 6.0 Material Non-stretched PET fiber 10%10% for 2nd 0.2 dtex × 3 mm layer Stretched PET fiber 90% 90% 0.1 dtex ×3 mm Manila hemp pulp — — Basis weight (g/m²) 2.0 6.0 Material PETbinder fiber 40% 40% for 3rd 1.7 dtex × 5 mm layer Non-stretched PETfiber 60% 60% 0.2 dtex × 3 mm Basis weight (g/m²) 6.0 6.0 Dryingtemperature (° C.) 110 110 Charac- Composite Basis weight (g/m²) 14.0217.98 teristics 1 Paper Density (g/cm³) 0.314 0.322 Tensile strength(kN/m) 0.50 0.52 Charac- 1st sheet Basis weight (g/m²) 7.05 8.96teristics 2 after Density (g/cm³) 0.257 0.298 delami- Tensile strength(kN/m) 0.20 0.27 nation Peel strength (N/m) 10.0 0.6 2nd sheet Basisweight (g/m²) 6.97 9.02 after Density (g/cm³) 0.260 0.302 delami-Tensile strength (kN/m) 0.18 0.23 nation

According to the present invention, reduction of basis weight of tissuepapers and heat-sensitive stencil printing masters can be realized,whilst there has been a limit in such a reduction with the conventionalmethods. According to the present invention, it is possible to produceheat-sensitive stencil printing masters having excellent inkpermeability at reduced costs. Further, according to the presentinvention, since a multi-layer paper having easy peelability gives twoor more tissue sheets, the productivity of tissue sheets issignificantly improved. The tissue sheets according to the presentinvention can be used as heat-sensitive stencil printing masters,filters and electric insulators.

1. A multi-layer paper comprising at least two paper layers combined bya paper making method, characterized in that said multi-layer paper hasat least one peelable paper layer interface having a peel strength of 10N/m or less, and in that said multi-layer paper is peelable into atleast two tissue sheets at said peelable paper layer interface.
 2. Amulti-layer paper as claimed in claim 1, wherein one of the two adjacentpaper-layers between which said peelable paper layer interface isdefined is mainly made of cellulose fibers, while the other paper layeris mainly made of synthetic fibers including binder fibers, said binderfibers exhibiting binder effect at a temperature of 90-120° C.
 3. Amulti-layer paper as claimed in claim 2, wherein said synthetic fibersare heteroatom-containing synthetic fibers.
 4. A multi-layer paper asclaimed in claim 2, wherein said synthetic fibers are polyolefin fibers.5. A multi-layer paper as claimed in claim 2, wherein said binder fibersare composite fibers and are contained in an amount of 20-100 mass %. 6.A multi-layer paper as claimed in claim 2, wherein said binder fibersare single-component fibers and are contained in an amount of 20-70 mass%.
 7. A multi-layer paper as claimed in claim 5, wherein said binderfibers are composite fibers having a core-sheath structure, said sheathbeing comprised of a resin exhibiting a binder effect at a temperatureof 90-120° C.
 8. A multi-layer paper as claimed in claim 7, wherein theresin constituting said sheath is a polyester resin.
 9. A multi-layerpaper as claimed in claim 7, wherein the resin constituting said sheathis a polyolefin resin or an ethylene-vinyl acetate copolymer resin. 10.A multi-layer paper as claimed in claim 1, wherein one of the twoadjacent paper layers between which said peelable paper layer interfaceis defined is made of synthetic fibers including composite binder fibershaving a low melting point component made of a polyolefin resin or anethylene-vinyl acetate copolymer resin, while the other paper layer ismade of synthetic fibers including composite binder fibers having a lowmelting point component made of a polyester resin, both of said binderfibers exhibiting binder effect at a temperature of 90-120° C.
 11. Amulti-layer paper as claimed in claim 10, wherein said one paper layermade of synthetic fibers including composite binder fibers having a lowmelting point component made of a polyolefin resin or an ethylene-vinylacetate copolymer resin is mainly made of polyolefin fibers, and whereinsaid binder fibers of said one paper layer exhibits binder effect at atemperature of 90-120° C. and is contained in an amount of 20-100 mass%.
 12. A multi-layer paper as claimed in claim 10, wherein said theother paper layer made of synthetic fibers including composite binderfibers having a low melting point component made of a polyester resin ismainly made of heteroatom-containing synthetic fibers, and wherein saidbinder fibers exhibit binder effect at a temperature of 90-120° C. andis contained in an amount of 20-100 mass %.
 13. A multi-layer paper asclaimed in claim 2, wherein said one layer mainly made of cellulosefibers contains a release agent.
 14. A multi-layer paper as claimed inclaim 2, wherein said the other layer mainly made of synthetic fibersare made of polyester fibers.
 15. A multi-layer paper as claimed inclaim 1, wherein one of the two adjacent paper layers between which saidpeelable interface is defined is made of relatively more highly orientedfibers as compared with that of the other paper layer.
 16. A multi-layerpaper as claimed in claim 1, wherein at least one of the two surfaces oftwo adjacent paper layers which surfaces define said peelable interfacehas been subjected to a smoothing treatment.
 17. A multi-layer paper asclaimed in claim 1, wherein at least one of said tissue sheet peeledfrom said multi-layer paper has a basis weight of 1-20 g/m².
 18. Amulti-layer paper as claimed in claim 2, wherein the tissue sheet peeledfrom said multi-layer paper and made of the synthetic fibers has adensity of not greater than 0.35 g/cm³.
 19. A multi-layer paper asclaimed in claim 3, wherein the tissue sheet peeled from saidmulti-layer paper and made of the heteroatom-containing synthetic fibershas a density of not greater than 0.35 g/cm³.
 20. A multi-layer papercomprising at least three paper layers unified by a paper making method,characterized in that said multi-layer paper has, as an intermediatelayer, at least one paper layer which can cause intralayer delaminationand which has a peel strength of 10 N/m or less, and in that saidmulti-layer paper is peelable into at least two tissue sheets at saidintermediate paper layer.
 21. A multi-layer paper as claimed in claim20, wherein each of the paper layers adjacent to said intermediate layeris mainly made of synthetic fibers including at least binder fibers,said binder fibers exhibiting binder effect at a temperature of 90-120°C.
 22. A multi-layer paper as claimed in claim 21, wherein said binderfibers are composite fibers and are contained in an amount of 20-100mass %.
 23. A multi-layer paper as claimed in claim 21, wherein saidbinder fibers are single-component fibers and are contained in an amountof 20-70 mass %.
 24. A multi-layer paper as claimed in claim 22, whereinsaid binder fibers are composite fibers having a core-sheath structure,said sheath being comprised of a resin exhibiting a binder effect at atemperature of 90-120° C.
 25. A multi-layer paper as claimed in claim20, wherein said paper layer which can cause intralayer delamination ismainly made of polyester fibers.
 26. A multi-layer paper as claimed inclaim 25, wherein said paper layer made of said polyester fibers has abasis weight of 2-8 g/m².
 27. A multi-layer paper as claimed in claim20, wherein said paper layer which can cause intralayer delamination ismainly made of cellulose fibers.
 28. A multi-layer paper as claimed inclaim 25, wherein said paper layer made of said cellulose fibers has abasis weight of 5-10 g/m².
 29. A method of forming tissue sheets,comprising providing a multi-layer paper according to claim 1, anddelaminating said multi-layer paper at said peelable paper layerinterface to obtain at least two tissue sheets.
 30. A method as claimedin claim 29, wherein at least one of said tissue sheets has a basisweight of 2-20 g/m².
 31. A method of forming tissue sheets, comprisingproviding a multi-layer paper according to claim 20, and delaminatingsaid multi-layer paper at said paper layer which can cause intralayerdelamination to obtain at least two tissue sheets.
 32. A method asclaimed in claim 31, wherein at least one of said tissue sheets has abasis weight of 2-20 g/m².
 33. A tissue sheet obtained by a methodaccording to claim 29 and having a basis weight of 2-20 g/m².
 34. Areinforced tissue sheet material, comprising a tissue sheet according toclaim 33 and a reinforcing member bonded thereto.
 35. A reinforcedtissue sheet material according to claim 34, wherein said reinforcingmember is a polymer film or a metal foil.
 36. A reinforced multi-layerpaper material, comprising a multi-layer paper according to claim 1 anda reinforcing member bonded to at least one of the both sides of saidmulti-layer paper.
 37. A reinforced multi-layer paper material accordingto claim 36, wherein said reinforcing member is a polymer film or ametal foil.
 38. A method of preparing a reinforced tissue sheetmaterial, comprising providing a reinforced multi-layer paper materialaccording to claim 36, and delaminating said multi-layer paper to obtaina reinforced tissue sheet material having said reinforcing member bondedthereto.
 39. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 1. 40. A material for producing a heat-sensitive stencil printingmaster, comprising a laminate obtained by bonding a thermoplasticpolymer film to at least one side of a multi-layer paper according toclaim
 1. 41. A heat-sensitive stencil printing master comprising aporous support, and a thermoplastic polymer film bonded to said poroussupport, wherein said porous support is a tissue paper according toclaim
 33. 42. A method of preparing a heat-sensitive stencil printingmaster, comprising a step of separating a tissue sheet from a materialaccording to claim 39, and a step of bonding a thermoplastic polymerfilm to the peeled surface of said separated thin sheet.
 43. A method ofpreparing a heat-sensitive stencil printing master, comprisingseparating, from said material according to claim 40, a laminate havingthe thin sheet to which said thermoplastic polymer film has been bonded.44. A multi-layer paper as claimed in claim 3, wherein said binderfibers are composite fibers and are contained in an amount of 20-100mass %.
 45. A multi-layer paper as claimed in claim 4, wherein saidbinder fibers are composite fibers and are contained in an amount of20-100 mass %.
 46. A multi-layer paper as claimed in claim 3, whereinsaid binder fibers are single-component fibers and are contained in anamount of 20-70 mass %.
 47. A multi-layer paper as claimed in claim 4,wherein said binder fibers are single-component fibers and are containedin an amount of 20-70 mass %.
 48. A multi-layer paper as claimed inclaim 3, wherein said one layer mainly made of cellulose fibers containsa release agent.
 49. A multi-layer paper as claimed in claim 4, whereinsaid one layer mainly made of cellulose fibers contains a release agent.50. A multi-layer paper as claimed in claim 5, wherein said one layermainly made of cellulose fibers contains a release agent.
 51. Amulti-layer paper as claimed in claim 6, wherein said one layer mainlymade of cellulose fibers contains a release agent.
 52. A multi-layerpaper as claimed in claim 7, wherein said one layer mainly made ofcellulose fibers contains a release agent.
 53. A multi-layer paper asclaimed in claim 8, wherein said one layer mainly made of cellulosefibers contains a release agent.
 54. A multi-layer paper as claimed inclaim 3, wherein said the other layer mainly made of synthetic fibersare made of polyester fibers.
 55. A multi-layer paper as claimed inclaim 4, wherein said the other layer mainly made of synthetic fibersare made of polyester fibers.
 56. A multi-layer paper as claimed inclaim 5, wherein said the other layer mainly made of synthetic fibersare made of polyester fibers.
 57. A multi-layer paper as claimed inclaim 6, wherein said the other layer mainly made of synthetic fibersare made of polyester fibers.
 58. A multi-layer paper as claimed inclaim 7, wherein said the other layer mainly made of synthetic fibersare made of polyester fibers.
 59. A multi-layer paper as claimed inclaim 8, wherein said the other layer mainly made of synthetic fibersare made of polyester fibers.
 60. A multi-layer paper as claimed inclaim 2, wherein one of the two adjacent paper layers between which saidpeelable interface is defined is made of relatively more highly orientedfibers as compared with that of the other paper layer.
 61. A multi-layerpaper as claimed in claim 3, wherein one of the two adjacent paperlayers between which said peelable interface is defined is made ofrelatively more highly oriented fibers as compared with that of theother paper layer.
 62. A multi-layer paper as claimed in claim 4,wherein one of the two adjacent paper layers between which said peelableinterface is defined is made of relatively more highly oriented fibersas compared with that of the other paper layer.
 63. A multi-layer paperas claimed in claim 5, wherein one of the two adjacent paper layersbetween which said peelable interface is defined is made of relativelymore highly oriented fibers as compared with that of the other paperlayer.
 64. A multi-layer paper as claimed in claim 6, wherein one of thetwo adjacent paper layers between which said peelable interface isdefined is made of relatively more highly oriented fibers as comparedwith that of the other paper layer.
 65. A multi-layer paper as claimedin claim 7, wherein one of the two adjacent paper layers between whichsaid peelable interface is defined is made of relatively more highlyoriented fibers as compared with that of the other paper layer.
 66. Amulti-layer paper as claimed in claim 8, wherein one of the two adjacentpaper layers between which said peelable interface is defined is made ofrelatively more highly oriented fibers as compared with that of theother paper layer.
 67. A multi-layer paper as claimed in claim 9,wherein one of the two adjacent paper layers between which said peelableinterface is defined is made of relatively more highly oriented fibersas compared with that of the other paper layer.
 68. A multi-layer paperas claimed in claim 10, wherein one of the two adjacent paper layersbetween which said peelable interface is defined is made of relativelymore highly oriented fibers as compared with that of the other paperlayer.
 69. A multi-layer paper as claimed in claim 11, wherein one ofthe two adjacent paper layers between which said peelable interface isdefined is made of relatively more highly oriented fibers as comparedwith that of the other paper layer.
 70. A multi-layer paper as claimedin claim 12, wherein one of the two adjacent paper layers between whichsaid peelable interface is defined is made of relatively more highlyoriented fibers as compared with that of the other paper layer.
 71. Amulti-layer paper as claimed in claim 13, wherein one of the twoadjacent paper layers between which said peelable interface is definedis made of relatively more highly oriented fibers as compared with thatof the other paper layer.
 72. A multi-layer paper as claimed in claim14, wherein one of the two adjacent paper layers between which saidpeelable interface is defined is made of relatively more highly orientedfibers as compared with that of the other paper layer.
 73. A multi-layerpaper as claimed in claim 2, wherein at least one of the two surfaces oftwo adjacent paper layers which surfaces define said peelable interfacehas been subjected to a smoothing treatment.
 74. A multi-layer paper asclaimed in claim 3, wherein at least one of the two surfaces of twoadjacent paper layers which surfaces define said peelable interface hasbeen subjected to a smoothing treatment.
 75. A multi-layer paper asclaimed in claim 4, wherein at least one of the two surfaces of twoadjacent paper layers which surfaces define said peelable interface hasbeen subjected to a smoothing treatment.
 76. A multi-layer paper asclaimed in claim 5, wherein at least one of the two surfaces of twoadjacent paper layers which surfaces define said peelable interface hasbeen subjected to a smoothing treatment.
 77. A multi-layer paper asclaimed in claim 6, wherein at least one of the two surfaces of twoadjacent paper layers which surfaces define said peelable interface hasbeen subjected to a smoothing treatment.
 78. A multi-layer paper asclaimed in claim 7, wherein at least one of the two surfaces of twoadjacent paper layers which surfaces define said peelable interface hasbeen subjected to a smoothing treatment.
 79. A multi-layer paper asclaimed in claim 8, wherein at least one of the two surfaces of twoadjacent paper layers which surfaces define said peelable interface hasbeen subjected to a smoothing treatment.
 80. A multi-layer paper asclaimed in claim 9, wherein at least one of the two surfaces of twoadjacent paper layers which surfaces define said peelable interface hasbeen subjected to a smoothing treatment.
 81. A multi-layer paper asclaimed in claim 10, wherein at least one of the two surfaces of twoadjacent paper layers which surfaces define said peelable interface hasbeen subjected to a smoothing treatment.
 82. A multi-layer paper asclaimed in claim 11, wherein at least one of the two surfaces of twoadjacent paper layers which surfaces define said peelable interface hasbeen subjected to a smoothing treatment.
 83. A multi-layer paper asclaimed in claim 12, wherein at least one of the two surfaces of twoadjacent paper layers which surfaces define said peelable interface hasbeen subjected to a smoothing treatment.
 84. A multi-layer paper asclaimed in claim 13, wherein at least one of the two surfaces of twoadjacent paper layers which surfaces define said peelable interface hasbeen subjected to a smoothing treatment.
 85. A multi-layer paper asclaimed in claim 14, wherein at least one of the two surfaces of twoadjacent paper layers which surfaces define said peelable interface hasbeen subjected to a smoothing treatment.
 86. A multi-layer paper asclaimed in claim 15, wherein at least one of the two surfaces of twoadjacent paper layers which surfaces define said peelable interface hasbeen subjected to a smoothing treatment.
 87. A multi-layer paper asclaimed in claim 2, wherein at least one of said tissue sheet peeledfrom said multi-layer paper has a basis weight of 1-20 g/m².
 88. Amulti-layer paper as claimed in claim 3, wherein at least one of saidtissue sheet peeled from said multi-layer paper has a basis weight of1-20 g/m².
 89. A multi-layer paper as claimed in claim 4, wherein atleast one of said tissue sheet peeled from said multi-layer paper has abasis weight of 1-20 g/m².
 90. A multi-layer paper as claimed in claim5, wherein at least one of said tissue sheet peeled from saidmulti-layer paper has a basis weight of 1-20 g/m².
 91. A multi-layerpaper as claimed in claim 6, wherein at least one of said tissue sheetpeeled from said multi-layer paper has a basis weight of 1-20 g/m². 92.A multi-layer paper as claimed in claim 7, wherein at least one of saidtissue sheet peeled from said multi-layer paper has a basis weight of1-20 g/m².
 93. A multi-layer paper as claimed in claim 8, wherein atleast one of said tissue sheet peeled from said multi-layer paper has abasis weight of 1-20 g/m².
 94. A multi-layer paper as claimed in claim9, wherein at least one of said tissue sheet peeled from saidmulti-layer paper has a basis weight of 1-20 g/m².
 95. A multi-layerpaper as claimed in claim 10, wherein at least one of said tissue sheetpeeled from said multi-layer paper has a basis weight of 1-20 g/m². 96.A multi-layer paper as claimed in claim 11, wherein at least one of saidtissue sheet peeled from said multi-layer paper has a basis weight of1-20 g/m².
 97. A multi-layer paper as claimed in claim 12, wherein atleast one of said tissue sheet peeled from said multi-layer paper has abasis weight of 1-20 g/m².
 98. A multi-layer paper as claimed in claim13, wherein at least one of said tissue sheet peeled from saidmulti-layer paper has a basis weight of 1-20 g/m².
 99. A multi-layerpaper as claimed in claim 14, wherein at least one of said tissue sheetpeeled from said multi-layer paper has a basis weight of 1-20 g/m². 100.A multi-layer paper as claimed in claim 15, wherein at least one of saidtissue sheet peeled from said multi-layer paper has a basis weight of1-20 g/m².
 101. A multi-layer paper as claimed in claim 16, wherein atleast one of said tissue sheet peeled from said multi-layer paper has abasis weight of 1-20 g/m².
 102. A multi-layer paper as claimed in claim3, wherein the tissue sheet peeled from said multi-layer paper and madeof the synthetic fibers has a density of not greater than 0.35 g/cm³.103. A multi-layer paper as claimed in claim 4, wherein the tissue sheetpeeled from said multi-layer paper and made of the synthetic fibers hasa density of not greater than 0.35 g/cm³.
 104. A multi-layer paper asclaimed in claim 5, wherein the tissue sheet peeled from saidmulti-layer paper and made of the synthetic fibers has a density of notgreater than 0.35 g/cm³.
 105. A multi-layer paper as claimed in claim 6,wherein the tissue sheet peeled from said multi-layer paper and made ofthe synthetic fibers has a density of not greater than 0.35 g/cm³. 106.A multi-layer paper as claimed in claim 7, wherein the tissue sheetpeeled from said multi-layer paper and made of the synthetic fibers hasa density of not greater than 0.35 g/cm³.
 107. A multi-layer paper asclaimed in claim 8, wherein the tissue sheet peeled from saidmulti-layer paper and made of the synthetic fibers has a density of notgreater than 0.35 g/cm³.
 108. A multi-layer paper as claimed in 21,wherein said paper layer which can cause intralayer delamination ismainly made of polyester fibers.
 109. A multi-layer paper as claimed in22, wherein said paper layer which can cause intralayer delamination ismainly made of polyester fibers.
 110. A multi-layer paper as claimed in23, wherein said paper layer which can cause intralayer delamination ismainly made of polyester fibers.
 111. A multi-layer paper as claimed in24, wherein said paper layer which can cause intralayer delamination ismainly made of polyester fibers.
 112. A multi-layer paper as claimed inclaim 21, wherein said paper layer which can cause intralayerdelamination is mainly made of cellulose fibers.
 113. A multi-layerpaper as claimed in claim 22, wherein said paper layer which can causeintralayer delamination is mainly made of cellulose fibers.
 114. Amulti-layer paper as claimed in claim 23, wherein said paper layer whichcan cause intralayer delamination is mainly made of cellulose fibers.115. A multi-layer paper as claimed in claim 24, wherein said paperlayer which can cause intralayer delamination is mainly made ofcellulose fibers.
 116. A method of forming tissue sheets, comprisingproviding a multi-layer paper according to claim 2, and delaminatingsaid multi-layer paper at said peelable paper layer interface to obtainat least two tissue sheets.
 117. A method of forming tissue sheets,comprising providing a multi-layer paper according to claim 3, anddelaminating said multi-layer paper at said peelable paper layerinterface to obtain at least two tissue sheets.
 118. A method of formingtissue sheets, comprising providing a multi-layer paper according toclaim 4, and delaminating said multi-layer paper at said peelable paperlayer interface to obtain at least two tissue sheets.
 119. A method offorming tissue sheets, comprising providing a multi-layer paperaccording to claim 5, and delaminating said multi-layer paper at saidpeelable paper layer interface to obtain at least two tissue sheets.120. A method of forming tissue sheets, comprising providing amulti-layer paper according to claim 6, and delaminating saidmulti-layer paper at said peelable paper layer interface to obtain atleast two tissue sheets.
 121. A method of forming tissue sheets,comprising providing a multi-layer paper according to claim 7, anddelaminating said multi-layer paper at said peelable paper layerinterface to obtain at least two tissue sheets.
 122. A method of formingtissue sheets, comprising providing a multi-layer paper according toclaim 8, and delaminating said multi-layer paper at said peelable paperlayer interface to obtain at least two tissue sheets.
 123. A method offorming tissue sheets, comprising providing a multi-layer paperaccording to claim 9, and delaminating said multi-layer paper at saidpeelable paper layer interface to obtain at least two tissue sheets.124. A method of forming tissue sheets, comprising providing amulti-layer paper according to claim 10, and delaminating saidmulti-layer paper at said peelable paper layer interface to obtain atleast two tissue sheets.
 125. A method of forming tissue sheets,comprising providing a multi-layer paper according to claim 11, anddelaminating said multi-layer paper at said peelable paper layerinterface to obtain at least two tissue sheets.
 126. A method of formingtissue sheets, comprising providing a multi-layer paper according toclaim 12, and delaminating said multi-layer paper at said peelable paperlayer interface to obtain at least two tissue sheets.
 127. A method offorming tissue sheets, comprising providing a multi-layer paperaccording to claim 13, and delaminating said multi-layer paper at saidpeelable paper layer interface to obtain at least two tissue sheets.128. A method of forming tissue sheets, comprising providing amulti-layer paper according to claim 14, and delaminating saidmulti-layer paper at said peelable paper layer interface to obtain atleast two tissue sheets.
 129. A method of forming tissue sheets,comprising providing a multi-layer paper according to claim 15, anddelaminating said multi-layer paper at said peelable paper layerinterface to obtain at least two tissue sheets.
 130. A method of formingtissue sheets, comprising providing a multi-layer paper according toclaim 16, and delaminating said multi-layer paper at said peelable paperlayer interface to obtain at least two tissue sheets.
 131. A method offorming tissue sheets, comprising providing a multi-layer paperaccording to claim 17, and delaminating said multi-layer paper at saidpeelable paper layer interface to obtain at least two tissue sheets.132. A method of forming tissue sheets, comprising providing amulti-layer paper according to claim 18, and delaminating saidmulti-layer paper at said peelable paper layer interface to obtain atleast two tissue sheets.
 133. A method of forming tissue sheets,comprising providing a multi-layer paper according to claim 19, anddelaminating said multi-layer paper at said peelable paper layerinterface to obtain at least two tissue sheets.
 134. A method of formingtissue sheets, comprising providing a multi-layer paper according toclaim 21, and delaminating said multi-layer paper at said paper layerwhich can cause intralayer delamination to obtain at least two tissuesheets.
 135. A method of forming tissue sheets, comprising providing amulti-layer paper according to claim 22, and delaminating saidmulti-layer paper at said paper layer which can cause intralayerdelamination to obtain at least two tissue sheets.
 136. A method offorming tissue sheets, comprising providing a multi-layer paperaccording to claim 23, and delaminating said multi-layer paper at saidpaper layer which can cause intralayer delamination to obtain at leasttwo tissue sheets.
 137. A method of forming tissue sheets, comprisingproviding a multi-layer paper according to claim 24, and delaminatingsaid multi-layer paper at said paper layer which can cause intralayerdelamination to obtain at least two tissue sheets.
 138. A method offorming tissue sheets, comprising providing a multi-layer paperaccording to claim 25, and delaminating said multi-layer paper at saidpaper layer which can cause intralayer delamination to obtain at leasttwo tissue sheets.
 139. A method of forming tissue sheets, comprisingproviding a multi-layer paper according to claim 26, and delaminatingsaid multi-layer paper at said paper layer which can cause intralayerdelamination to obtain at least two tissue sheets.
 140. A method offorming tissue sheets, comprising providing a multi-layer paperaccording to claim 27, and delaminating said multi-layer paper at saidpaper layer which can cause intralayer delamination to obtain at leasttwo tissue sheets.
 141. A method of forming tissue sheets, comprisingproviding a multi-layer paper according to claim 28, and delaminatingsaid multi-layer paper at said paper layer which can cause intralayerdelamination to obtain at least two tissue sheets.
 142. A tissue sheetobtained by a method according to claim 30 and having a basis weight of2-20 g/m².
 143. A tissue sheet obtained by a method according to claim31 and having a basis weight of 2-20 g/m².
 144. A tissue sheet obtainedby a method according to claim 32 and having a basis weight of 2-20g/m².
 145. A reinforced multi-layer paper material, comprising amulti-layer paper according to claim 2 and a reinforcing member bondedto at least one of the both sides of said multi-layer paper.
 146. Areinforced multi-layer paper material, comprising a multi-layer paperaccording to claim 3 and a reinforcing member bonded to at least one ofthe both sides of said multi-layer paper.
 147. A reinforced multi-layerpaper material, comprising a multi-layer paper according to claim 4 anda reinforcing member bonded to at least one of the both sides of saidmulti-layer paper.
 148. A reinforced multi-layer paper material,comprising a multi-layer paper according to claim 5 and a reinforcingmember bonded to at least one of the both sides of said multi-layerpaper.
 149. A reinforced multi-layer paper material, comprising amulti-layer paper according to claim 6 and a reinforcing member bondedto at least one of the both sides of said multi-layer paper.
 150. Areinforced multi-layer paper material, comprising a multi-layer paperaccording to claim 7 and a reinforcing member bonded to at least one ofthe both sides of said multi-layer paper.
 151. A reinforced multi-layerpaper material, comprising a multi-layer paper according to claim 8 anda reinforcing member bonded to at least one of the both sides of saidmulti-layer paper.
 152. A reinforced multi-layer paper material,comprising a multi-layer paper according to claim 9 and a reinforcingmember bonded to at least one of the both sides of said multi-layerpaper.
 153. A reinforced multi-layer paper material, comprising amulti-layer paper according to claim 10 and a reinforcing member bondedto at least one of the both sides of said multi-layer paper.
 154. Areinforced multi-layer paper material, comprising a multi-layer paperaccording to claim 11 and a reinforcing member bonded to at least one ofthe both sides of said multi-layer paper.
 155. A reinforced multi-layerpaper material, comprising a multi-layer paper according to claim 12 anda reinforcing member bonded to at least one of the both sides of saidmulti-layer paper.
 156. A reinforced multi-layer paper material,comprising a multi-layer paper according to claim 13 and a reinforcingmember bonded to at least one of the both sides of said multi-layerpaper.
 157. A reinforced multi-layer paper material, comprising amulti-layer paper according to claim 14 and a reinforcing member bondedto at least one of the both sides of said multi-layer paper.
 158. Areinforced multi-layer paper material, comprising a multi-layer paperaccording to claim 15 and a reinforcing member bonded to at least one ofthe both sides of said multi-layer paper.
 159. A reinforced multi-layerpaper material, comprising a multi-layer paper according to claim 16 anda reinforcing member bonded to at least one of the both sides of saidmulti-layer paper.
 160. A reinforced multi-layer paper material,comprising a multi-layer paper according to claim 17 and a reinforcingmember bonded to at least one of the both sides of said multi-layerpaper.
 161. A reinforced multi-layer paper material, comprising amulti-layer paper according to claim 18 and a reinforcing member bondedto at least one of the both sides of said multi-layer paper.
 162. Areinforced multi-layer paper material, comprising a multi-layer paperaccording to claim 19 and a reinforcing member bonded to at least one ofthe both sides of said multi-layer paper.
 163. A reinforced multi-layerpaper material, comprising a multi-layer paper according to claim 20 anda reinforcing member bonded to at least one of the both sides of saidmulti-layer paper.
 164. A reinforced multi-layer paper material,comprising a multi-layer paper according to claim 21 and a reinforcingmember bonded to at least one of the both sides of said multi-layerpaper.
 165. A reinforced multi-layer paper material, comprising amulti-layer paper according to claim 22 and a reinforcing member bondedto at least one of the both sides of said multi-layer paper.
 166. Areinforced multi-layer paper material, comprising a multi-layer paperaccording to claim 23 and a reinforcing member bonded to at least one ofthe both sides of said multi-layer paper.
 167. A reinforced multi-layerpaper material, comprising a multi-layer paper according to claim 24 anda reinforcing member bonded to at least one of the both sides of saidmulti-layer paper.
 168. A reinforced multi-layer paper material,comprising a multi-layer paper according to claim 25 and a reinforcingmember bonded to at least one of the both sides of said multi-layerpaper.
 169. A reinforced multi-layer paper material, comprising amulti-layer paper according to claim 26 and a reinforcing member bondedto at least one of the both sides of said multi-layer paper.
 170. Areinforced multi-layer paper material, comprising a multi-layer paperaccording to claim 27 and a reinforcing member bonded to at least one ofthe both sides of said multi-layer paper.
 171. A reinforced multi-layerpaper material, comprising a multi-layer paper according to claim 28 anda reinforcing member bonded to at least one of the both sides of saidmulti-layer paper.
 172. A method of preparing a reinforced tissue sheetmaterial, comprising providing a reinforced multi-layer paper materialaccording to claim 37, and delaminating said multi-layer paper to obtaina reinforced tissue sheet material having said reinforcing member bondedthereto.
 173. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 2. 174. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 3. 175. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 4. 176. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 5. 177. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 6. 178. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 7. 179. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 8. 180. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 9. 181. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 10. 182. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 11. 183. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 12. 184. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 13. 185. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 14. 186. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 15. 187. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 16. 188. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 17. 189. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 18. 190. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 19. 191. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 20. 192. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 21. 193. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 22. 194. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 23. 195. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 24. 196. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 25. 197. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 26. 198. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 27. 199. A porous support material for producing a heat-sensitivestencil printing master, comprising a multi-layer paper according toclaim
 28. 200. A material for producing a heat-sensitive stencilprinting master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 2. 201. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 3. 202. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 4. 203. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 5. 204. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 6. 205. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 7. 206. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 8. 207. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 9. 208. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 10. 209. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 11. 210. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 12. 211. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 13. 212. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 14. 213. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 15. 214. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 16. 215. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 17. 216. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 18. 217. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 19. 218. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 20. 219. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 21. 220. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 22. 221. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 23. 222. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 24. 223. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 25. 224. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 26. 225. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim
 27. 226. A material for producing a heat-sensitivestencil printing master, comprising a laminate obtained by bonding athermoplastic polymer film to at least one side of a multi-layer paperaccording to claim 28.